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19 pages, 17403 KiB

Open AccessArticle

Tensile Properties and Fracture Analysis of Duplex (2205) and Super Duplex (2507) Stainless Steels, Produced via Laser Powder Bed Fusion Additive Manufacturing

by Leonidas Karavias, Leonidas Gargalis, Joachim Seland Graff, Marius Johansen, Spyros Diplas and Evaggelia K. Karaxi

Metals 2024, 14(7), 838; https://doi.org/10.3390/met14070838 - 22 Jul 2024

Viewed by 728

Abstract

Additive manufacturing of duplex (DSS) and super duplex stainless steel (SDSS) has been successfully demonstrated using laser powder bed fusion (LPBF) in recent years. Owing to the high cooling rates, as-built LPBF-processed DSS and SDSS exhibit close to 100% ferritic microstructures and require [...] Read more.

Additive manufacturing of duplex (DSS) and super duplex stainless steel (SDSS) has been successfully demonstrated using laser powder bed fusion (LPBF) in recent years. Owing to the high cooling rates, as-built LPBF-processed DSS and SDSS exhibit close to 100% ferritic microstructures and require heat treatment at 1000–1300 °C to obtain the desired duplex microstructure. In this work, the mechanical properties of DSS and SDSS processed via LPBF were investigated in three building directions (vertical, horizontal, diagonal) and three processing conditions (as-built, stress-relieved, annealed, and quenched) using uniaxial tensile testing. As-built samples exhibited tensile and yield strength greater than 1000 MPa accompanied by less than 20% elongation at break. In comparison, the water-quenched samples and samples annealed at 1100 °C exhibited elongation at break greater than 34% with yield and tensile strength values less than 950 MPa. Stress relief annealing at 300 °C had a negligible impact on the mechanical properties. Austenite formation upon high-temperature annealing restored the reduced ductility of the as-built samples. The as-built and stress-relieved SDSS showed the highest yield and tensile strength values in the horizontal build direction, reaching up to ≈1400 and ≈1500 MPa (for SDSS), respectively, as compared to the vertical and diagonal directions. Fractographic investigation after tensile testing revealed predominantly a quasi-ductile failure mechanism, showing fine size dimple formation and cleavage facets in the as-built state and a fully ductile fracture in the annealed and quenched conditions. The findings in this study demonstrate the mechanical anisotropy of DSS and SDSS along three different build orientations, 0°, 45°, 90°, and three post-processing conditions. Full article

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13 pages, 9194 KiB

Open AccessArticle

Effect of Calefaction and Stress Relaxation on Grain Boundaries/Textures of Cu–Cr–Ni Alloy

by Haitao Liu, Guojie Wang, Kexing Song, Yunxiao Hua, Yong Liu and Tao Huang

Metals 2024, 14(7), 837; https://doi.org/10.3390/met14070837 - 22 Jul 2024

Viewed by 536

Abstract

The Cu–Cr–Ni alloy is a key material for the manufacturing of connectors, which requires excellent resistance to stress relaxation. However, the inherent correlation among microstructure, texture, and properties is still unclear. In this study, we investigated the influence of calefaction and stress relaxation [...] Read more.

The Cu–Cr–Ni alloy is a key material for the manufacturing of connectors, which requires excellent resistance to stress relaxation. However, the inherent correlation among microstructure, texture, and properties is still unclear. In this study, we investigated the influence of calefaction and stress relaxation on the grain boundaries (GBs), textures, and properties of the Cu–Cr–Ni alloy. The results showed that calefaction and stress relaxation had opposite effects on GBs and textures. Calefaction led to a decrease in the proportion of low-angle grain boundaries (LAGBs), an increase in the Schmidt factor (SF) value of the grains, and a transition of texture from <111> to <113>. The grains with higher SF values were more susceptible to plastic deformation, which deteriorated the stress relaxation resistance. By comparison, stress relaxation led to an increase in the proportion of LAGBs, a decrease in SF values of the grains, and a transition of texture from <113> to <111> and <001>. After stress relaxation, the variation trends of the GBs and textures were consistent with those of other plastic deformations, indicating that stress relaxation can be verified by the variations in GBs and textures. Our findings provide a theoretical basis for improvements in stress relaxation resistance of the Cu-based alloys used in connector industry. Full article

(This article belongs to the Special Issue New Horizons in Experimental Synthesis and Characterization of Advanced Metallic Nanomaterials and Nanocomposites for Energy Storage and Conversion)

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15 pages, 18492 KiB

Open AccessArticle

Mechanical Properties and Wear Resistance of Biodegradable ZnMgY Alloy

by Nicanor Cimpoesu, Viorel Paleu, Catalin Panaghie, Ana-Maria Roman, Alin Marian Cazac, Lucian-Ionel Cioca, Costica Bejinariu, Stefan Constantin Lupescu, Mihai Axinte, Mihai Popa and Georgeta Zegan

Metals 2024, 14(7), 836; https://doi.org/10.3390/met14070836 - 22 Jul 2024

Viewed by 572

Abstract

Biodegradable metallic materials are gaining attention for medical applications in short-term implants (15–500 days) because of their good mechanical properties, biocompatibility, and generalized corrosion. Most medical applications involve implant wear processes, particularly for bone fractures. Parallelepipedic specimens (dimensions 50 mm × 10 mm [...] Read more.

Biodegradable metallic materials are gaining attention for medical applications in short-term implants (15–500 days) because of their good mechanical properties, biocompatibility, and generalized corrosion. Most medical applications involve implant wear processes, particularly for bone fractures. Parallelepipedic specimens (dimensions 50 mm × 10 mm × 3 mm) were obtained by cutting the hot-rolled material processed from cast ingots of ZnMgY. To test the tribological performance of these stationary specimens, they were placed at the upper point of the machine’s tribological contact. The rotating lower disk of the AMSLER machine (AMSLER & Co., Schaffhouse, Switzerland) is manufactured from AISI 52100 bearing steel with a 62–65 HRC hardness and a diameter of 59 mm both radially and axially. Frictional torque is the parameter that is measured. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to analyze the worn areas. The material behavior in the normal and wear states upon immersion in simulated body fluid (SBF) was evaluated. Full article

(This article belongs to the Section Biobased and Biodegradable Metals)

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17 pages, 7917 KiB

Open AccessArticle

Study of Size Effect on Ni₆₀Nb₄₀ Amorphous Particles and Thin Films by Molecular Dynamic Simulations

by Wenbiao Zhang and Yungui Ma

Metals 2024, 14(7), 835; https://doi.org/10.3390/met14070835 - 22 Jul 2024

Viewed by 528

Abstract

Ni₆₀Nb₄₀ amorphous particles (APs) and amorphous thin films (ATFs) with various sizes were investigated by molecular dynamic simulations. It is revealed that sample size has effects on both Ni₆₀Nb₄₀ APs and ATFs composed of shell or surface [...] Read more.

Ni₆₀Nb₄₀ amorphous particles (APs) and amorphous thin films (ATFs) with various sizes were investigated by molecular dynamic simulations. It is revealed that sample size has effects on both Ni₆₀Nb₄₀ APs and ATFs composed of shell or surface and core components. Ni₆₀Nb₄₀ APs have an average bond length of 2.57 Å with major fivefold-symmetry atomic packing and low bond-orientation orders of Q₆ and Q₄ in both core and shell components. Ni atoms in Ni₆₀Nb₄₀ APs and ATFs prefer to segregate to the shell and surface regions, respectively. Atomic packing structure differences between various-sized Ni₆₀Nb₄₀ APs and ATFs affect their glass transition temperatures T_g, i.e., T_g decreases as the particle size or the film thickness decreases in Ni₆₀Nb₄₀ APs and ATFs, respectively. Our obtained results for Ni₆₀Nb₄₀ APs and ATFs clearly reveal a size effect on atomic packing and glass transition temperature in low-dimensional metallic glass systems. Full article

(This article belongs to the Special Issue Simulation and Optimization Methods in Machining and Structure/Material Design)

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22 pages, 6954 KiB

Open AccessArticle

Development of a Flow Rule Based on a Unified Plasticity Model for 13Cr-4Ni Low-Carbon Martensitic Stainless Steel Subject to Post-Weld Heat Treatment

by Mir Mehrdad Hosseini, Jacques Lanteigne, Carlo Baillargeon, Mohammad Jahazi and Henri Champliaud

Metals 2024, 14(7), 834; https://doi.org/10.3390/met14070834 - 21 Jul 2024

Viewed by 663

Abstract

This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal [...] Read more.

This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal and surrounding areas of the base metal near welded joints. The evolving inelastic strain rate with reformed austenite led to defining two distinct flow rules in the pure martensitic (α′) and austenitic (γ) phases. A linear rule of mixture was then applied to assess global effective stress based on the inelastic strain rate and current austenite fraction during the PWHT. A unified constitutive model incorporating drag stress and back stress, evolving with creep and plastic deformation mechanisms during the PWHT, described the stress–strain behavior. To validate this analysis, a third flow rule was determined in the 18% tempered austenitic microstructure, compared with the rule of mixture’s effective stress contribution from each phase on the inelastic strain rate. Isothermal constant strain rate tests in stabilized crystalline microstructures evaluated constants specific to their respective flow rules. This study demonstrates the stability of reformed austenite at elevated temperatures during slow cooling and its significant influence on the mechanical properties of 13Cr-4Ni steels. The effectiveness of estimating yield stress using the rule of mixture based on individual phase behaviors is also confirmed. Full article

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28 pages, 8146 KiB

Open AccessArticle

Synthesis-Dependent Structural and Magnetic Properties of Monodomain Cobalt Ferrite Nanoparticles

by Aleksandra Milutinović, Zorica Ž. Lazarević, Marija Šuljagić and Ljubica Andjelković

Metals 2024, 14(7), 833; https://doi.org/10.3390/met14070833 - 20 Jul 2024

Viewed by 909

Abstract

This research examines the structural and magnetic properties of monodomain cobalt ferrite nanoparticles with the formula (Co_1−xFe_x)^A[Fe_2−xCo_x]^BO₄. The particles were synthesized using various methods, including coprecipitation (with [...] Read more.

This research examines the structural and magnetic properties of monodomain cobalt ferrite nanoparticles with the formula (Co_1−xFe_x)^A[Fe_2−xCo_x]^BO₄. The particles were synthesized using various methods, including coprecipitation (with and without ultrasonic assistance), coprecipitation followed by mechanochemical treatment, microemulsion, and microwave-assisted hydrothermal techniques. The resulting materials were extensively analyzed using X-ray diffraction (XRD) and magnetic measurements to investigate how different synthesis methods affect the structure and cation distribution in nanoscale CoFe₂O₄. For particles ranging from 15.8 to 19.0 nm in size, the coercivity showed a near-linear increase from 302 Oe to 1195 Oe as particle size increased. Saturation magnetization values fell between 62.6 emu g⁻¹ and 74.3 emu g⁻¹, primarily influenced by the inversion coefficient x (0.58–0.85). XRD analysis revealed that as the larger Co²⁺ cations migrate from B- to A-sites (decreasing x), the lattice constants and inter-cation hopping distances increase, while the average strength of super-exchange interactions decreases. This study establishes a connection between the magnetic properties of the synthesized samples and their structural features. Importantly, this research demonstrates that careful selection of the synthesis method can be used to control the magnetic properties of these nanoparticles. Full article

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20 pages, 8775 KiB

Open AccessArticle

Continuous Casting Preparation Process of Helical Fiber-Reinforced Metal Matrix Composites

by Hui Yang, Ming Chang and Chunjing Wu

Metals 2024, 14(7), 832; https://doi.org/10.3390/met14070832 - 20 Jul 2024

Viewed by 521

Abstract

To improve the strength of the metal while maintaining good plasticity, helical fibers are added to the metal matrix. How to form helical fiber and control its parameters in the preparation process are urgent problems to be solved in the study of helical [...] Read more.

To improve the strength of the metal while maintaining good plasticity, helical fibers are added to the metal matrix. How to form helical fiber and control its parameters in the preparation process are urgent problems to be solved in the study of helical fiber-reinforced metal matrix composites. In this paper, the continuous casting process of helical fiber-reinforced metal matrix composites was proposed. To reduce the difficulty of the experiment, the formation process of helical fiber on metal matrix and the relationship between the continuous casting process parameters and helical shape fiber parameters were studied by preparing helical carbon fiber-reinforced lead matrix composites with a low-melting-point metal matrix. The results show that this process can produce helical fiber-reinforced metal matrix composite stably and continuously, and the helical shape parameters of the composite can be controlled by changing the process parameters of continuous casting. To further improve the practical application of this process, helical carbon fiber-reinforced aluminum matrix composites were prepared. The test result in terms of mechanical property shows that the tensile strength and elongation of the composite were improved. This indicates that the reinforced phase of the helical structure of the metal matrix composite has higher strength and toughness compared with the matrix metal. Full article

(This article belongs to the Special Issue Metal Matrix Composites: Fabrication, Mechanical Properties and Application)

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22 pages, 6423 KiB

Open AccessArticle

Investigation of the Solid Solution Hardening Mechanism of Low-Alloyed Copper–Scandium Alloys

by Ramona Henle, Simon Kött, Norbert Jost, Gerrit Nandi, Julia Dölling, Andreas Zilly and Ulrich Prahl

Metals 2024, 14(7), 831; https://doi.org/10.3390/met14070831 - 20 Jul 2024

Viewed by 1890

Abstract

The addition of alloying elements is a crucial factor in improving the mechanical properties of pure copper, particularly in terms of enhancing its yield strength and hardness. This study examines the influence of scandium additions (up to 0.27 wt.%) on low-alloyed copper. Following [...] Read more.

The addition of alloying elements is a crucial factor in improving the mechanical properties of pure copper, particularly in terms of enhancing its yield strength and hardness. This study examines the influence of scandium additions (up to 0.27 wt.%) on low-alloyed copper. Following the casting and solution-annealing processes, the alloys were quenched in water to maintain a supersaturated state. The mechanical properties were evaluated by tensile tests to measure the yield strength and the dynamic resonance method to determine the modulus of rigidity. Additionally, X-ray diffraction was utilized to analyze changes in lattice parameters, elucidating the structural modifications induced by scandium. This study dissects the parelastic and dielastic effects underlying the solid solution hardening mechanism, providing insights into how scandium alters copper’s mechanical properties. The findings align with the solid solution hardening theories proposed by Fleischer and Labusch, providing a comprehensive understanding of the observed phenomena. Full article

(This article belongs to the Special Issue Mechanical Behaviors and Interfacial Segregation Phenomena in Metallic Materials: Simulation, Theory, and Characterization)

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18 pages, 18967 KiB

Open AccessArticle

Numerical Study on Fretting Wear of DZ125/FGH99 Tenon/Mortise Joint Structure

by Laicong Song, Zhenyu Shi, Chengpeng Zhang and Yong Li

Metals 2024, 14(7), 830; https://doi.org/10.3390/met14070830 - 19 Jul 2024

Viewed by 672

Abstract

Fretting wear in the contact area between the aero-engine blade tenon and turbine disk mortise has an important influence on the performance of the aero-engine. In this paper, the tenon joint structure of the DZ125/FGH99 superalloy material is taken as the research object, [...] Read more.

Fretting wear in the contact area between the aero-engine blade tenon and turbine disk mortise has an important influence on the performance of the aero-engine. In this paper, the tenon joint structure of the DZ125/FGH99 superalloy material is taken as the research object, and the finite element model of the fir-tree tenon joint structure is established. Through subroutine invocation and mesh adaptive control technology, the fretting wear problem of dissimilar material contact pairs under composite load is numerically studied. The results show that for the specific tenon joint structure and load and boundary conditions studied in this paper, the maximum wear occurs on the contact surface of the first tooth, and the surface will show different partial slip states in different load cycles. The slip region always extends from the two contact edges to the interior, and the upper side has a larger range. Wear has a significant effect on the stress distribution and stick–slip state of the contact surface. The second and third teeth have a small amount of wear and are basically in a stick state during the entire wear process. Therefore, wear has little effect on the stress distribution and the stick–slip state of the contact surface. This study reveals the coupling relationship between the fretting wear and contact state of the tenon joint structure. Full article

(This article belongs to the Special Issue Green Hybrid Machining Technology for Difficult-Machining Metal Materials)

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12 pages, 3883 KiB

Open AccessArticle

A Case Study of a Laser Beam Welding Model for the Welding of Inconel 718 Sheets of a Dissimilar Thickness

by Oihane Murua, Jon Iñaki Arrizubieta, Aitzol Lamikiz and Heinz Ingo Schneider

Metals 2024, 14(7), 829; https://doi.org/10.3390/met14070829 - 19 Jul 2024

Viewed by 690

Abstract

Laser beam welding (LBW) is a highly demanded process for premium-quality joints in aeronautic, energy, or industrial sectors, where flexibility and low-heat-affected zones are required. One of the main applications of LBW in the near future is expected to be the welding of [...] Read more.

Laser beam welding (LBW) is a highly demanded process for premium-quality joints in aeronautic, energy, or industrial sectors, where flexibility and low-heat-affected zones are required. One of the main applications of LBW in the near future is expected to be the welding of new turbine engine components, which are typically made of Nickel-based superalloys. However, parameter setup is time- and resource-consuming, where experiment-based methods are typically employed. Therefore, the process development is far from an efficient resource utilization. In the present work, an LBW numerical model is developed and experimentally validated through a machine-integrated monitoring system. The LBW model is based on solving the heat transfer problem produced by the laser and provides the resulting temperature field, as well as the weld bead dimensions. The model includes a variable heat source that automatically adapts to the welding regime, conduction, or keyhole. For the model validation, two Inconel 718 sheets of different thicknesses are butt-welded and an error of around 10% is obtained, which ensures the validity of the model. Full article

(This article belongs to the Special Issue Numerical Simulation of Metals Welding Process—2nd Edition)

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19 pages, 11907 KiB

Open AccessFeature PaperArticle

Examination of Novel Titanium-639 Alloy as a Means of Balancing Strength and Ductility through Molybdenum Addition Rather than Prolonged Aging Heat Treatment

by Shiraz Mujahid, Alireza Fadavi Boostani, YubRaj Paudel, Andrew Oppedal, Bhasker Paliwal, Hongjoo Rhee and Haitham El Kadiri

Metals 2024, 14(7), 828; https://doi.org/10.3390/met14070828 - 18 Jul 2024

Viewed by 662

Abstract

Manufacturing titanium alloys with simultaneous enhancement in strength and ductility has motivated extensive research into various strategies for regulating the arrangement and texture of α and β phases. The present study explores a novel α + β titanium alloy, TIMETAL 639 (Ti-639), produced [...] Read more.

Manufacturing titanium alloys with simultaneous enhancement in strength and ductility has motivated extensive research into various strategies for regulating the arrangement and texture of α and β phases. The present study explores a novel α + β titanium alloy, TIMETAL 639 (Ti-639), produced by replacing a portion of vanadium in Ti-64 with molybdenum. The low diffusivity and β-stabilizing effects of molybdenum help retain bimodal characteristics within solution heat-treated Ti-639 microstructures. EBSD and TEM were used to examine β-phase evolution after thermal processing and recrystallization of new globular α grains within pre-existing colonies in a depleted bimodal microstructure. These depleted bimodal colonies in solution heat-treated Ti-639 also led to lower misorientation spreads and dislocation densities within neighboring primary α grains. Quasi-static compression along the plate normal direction demonstrated the ability of the depleted bimodal microstructure to simultaneously enhance strength and ductility in Ti-639 (~90 MPa stronger, ~6% higher failure strain) versus identically processed Ti-64. Only one solution heat-treatment step (1 h at 900 °C) is needed to achieve these properties in Ti-639, whereas comparable properties in Ti-64 required prolonged aging heat treatment (24 h at 600 °C) after the same solution heat-treatment step, making Ti-639 a viable α + β alloy candidate. Full article

(This article belongs to the Special Issue Alloy Design and Its Performance Trade-Offs)

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14 pages, 20687 KiB

Open AccessArticle

Effect of Silicon on the Martensitic Nucleation and Transformation of 301 Stainless Steel under Various Cold-Rolling Deformations

by Jun Li, Yaji Li, Jian Wang and Peide Han

Metals 2024, 14(7), 827; https://doi.org/10.3390/met14070827 - 18 Jul 2024

Viewed by 596

Abstract

A systematic study was conducted on the influence of silicon on the microstructure, stress distribution, and martensitic nucleation and transformation of 301 metastable austenitic stainless steel during cold-rolling deformation. When the deformation amount of conventional 301 stainless steel is ≤20%, the amount of [...] Read more.

A systematic study was conducted on the influence of silicon on the microstructure, stress distribution, and martensitic nucleation and transformation of 301 metastable austenitic stainless steel during cold-rolling deformation. When the deformation amount of conventional 301 stainless steel is ≤20%, the amount of martensite transformation is very small. When the deformation amount is ≥30%, the amount of martensite transformation significantly increases. The introduction of Si significantly improves the amount of martensite transformation and the uniformity of deformation. 301Si-H has a significantly higher amount of martensite in the same deformation microstructure than conventional 301Si-L with a lower silicon content. Increasing the Si content decreases the stacking fault energy of 301 stainless steel. During deformation, Si tends to cluster at the grain boundaries, reducing stacking fault width and increasing dislocation density, creating sites for shear martensite nucleation at the grain boundaries. Simultaneously, significant deformation encourages the formation of deformation twins and facilitates martensite nucleation. Full article

(This article belongs to the Special Issue Advances in Metal Rolling Processes)

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11 pages, 6916 KiB

Open AccessArticle

Role of Stabilization Heat Treatment Inducing γ′-γ″ Co-Precipitates and η Phase on Tensile Behaviors of Inconel 706

by Chenglu Liu, Lei Gao, Hao Wu, Kesong Miao, He Wu, Rengeng Li and Xuewen Li

Metals 2024, 14(7), 826; https://doi.org/10.3390/met14070826 - 18 Jul 2024

Viewed by 537

Abstract

Inconel 706 (IN706) alloy is commonly used in aircraft engines and power plant components that must meet very high performance requirements. The stabilization treatment has a significant effect on the precipitation and evolution of the reinforcing phases of the alloy, favoring the creep [...] Read more.

Inconel 706 (IN706) alloy is commonly used in aircraft engines and power plant components that must meet very high performance requirements. The stabilization treatment has a significant effect on the precipitation and evolution of the reinforcing phases of the alloy, favoring the creep properties and adversely affecting the room-temperature tensile properties. However, the mechanism of the effect of the stabilization treatment on the mechanical properties of the alloys remains unclear. In this study, the effect of stabilization treatment time on the microstructure and tensile properties of IN706 alloy was investigated. The results showed that as the stabilization time gradually increased, the tensile strength remained basically unchanged (about 1250 MPa), the yield strength decreased from 1031 MPa to 985 MPa, and the plasticity decreased from 28.2% to 20.2%. The stabilization treatment induces the precipitation of granular, rod-shaped, and needle-like η phases at grain boundaries, accompanied by the appearance of a precipitate free zone (PFZ). Since the η phase is enriched with Ti and Nb, its precipitation along the grain boundary results in the depletion of Ti and Nb in the surrounding regions, thereby constraining the precipitation of the γ′ and γ″ phases, resulting in the appearance of PFZ. With increasing stabilization time, the size increase and volume fraction decrease in γ′-γ″ co-precipitates due to the precipitation of η-phase precipitates, leading to a decrease in their yield strength. Combined with in situ tensile tests, it was found that the decrease in the elongation of the stabilization treatment samples was due to the presence of η phase at the grain boundaries, which induced stress concentration and cracking at the grain boundaries. The results show that the mechanical properties of the material were gradually enhanced as the stabilization time decreased. This means it can help to choose the suitable process for IN706 alloy in different service conditions. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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21 pages, 14661 KiB

Open AccessArticle

Research on Multiscale Numerical Simulation Method for SLM Melting Process

by Fan Zou, Shuguang Yao, Yunhui Dong, Xin Zheng, Minhan Xie, Lei Yang and Dongtao Wang

Metals 2024, 14(7), 825; https://doi.org/10.3390/met14070825 - 18 Jul 2024

Viewed by 653

Abstract

In the selective-laser-melting process, it is difficult to monitor the evolution of the melt pool in real time via experimental methods due to the complexity and fine scale of laser–powder interaction; numerical simulation has become an important technical way to study the selective-laser-melting [...] Read more.

In the selective-laser-melting process, it is difficult to monitor the evolution of the melt pool in real time via experimental methods due to the complexity and fine scale of laser–powder interaction; numerical simulation has become an important technical way to study the selective-laser-melting process. A coupled thermal–fluid model of the SLM single-layer melt-channel-forming process is constructed based on hydrodynamic theory for AlSi10Mg metallic materials, and the SLM single-layer melt-channel-forming process is investigated by combining parametric experiments and numerical simulation methods. A binarised spatial-random-function pore material model is proposed, and a multiscale finite-element numerical model of the melt-channel-forming process is constructed to compare and verify the first-layer melt-channel-forming process and to analyse the evolution of the melt pool and the change in the temperature field in multi-layer melt channel formation. The results of this study show that the multiscale numerical model of the SLM multilayer melt-channel-forming process has a reliable computational accuracy, with an average error of 6.77% for the melt pool length and 1.69% for the melt pool width; Marangoni convection effects increase the melt pool size, and the presence of pores significantly affects the evolution of the powder bed temperature field. With laser scanning and powder bed stacking, the overall temperature of the powder bed and the peak temperature of the molten pool gradually increased, and the length, width, and height dimensions of the molten pool increased by 44.9%, 21.7%, and 33.8%, respectively. Full article

(This article belongs to the Section Additive Manufacturing)

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13 pages, 6805 KiB

Open AccessArticle

High–Strength Porous TiNbZrTaFe Alloys Fabricated by Sintering of Nanocomposite Powder Precursor with Space Holder Technique

by Yuhua Li, Yuxin He, Rong Zhao, Libin Niu, Juxin Qu and Lai-Chang Zhang

Metals 2024, 14(7), 824; https://doi.org/10.3390/met14070824 - 18 Jul 2024

Viewed by 736

Abstract

Although introducing high porosity in biomedical Ti alloys can reduce their elastic modulus and promote new bone ingrowth, relieving the stress–shielding effect and implant failure, this also causes a decline in the alloys’ mechanical strength. In this work, a new preparation method for [...] Read more.

Although introducing high porosity in biomedical Ti alloys can reduce their elastic modulus and promote new bone ingrowth, relieving the stress–shielding effect and implant failure, this also causes a decline in the alloys’ mechanical strength. In this work, a new preparation method for the high–strength and high–porosity Ti₆₅Nb_23.33Zr₅Ta_1.67Fe₅ (TNZTF, at.%) alloy was suggested by sintering nanocomposite powder precursor in combination with the use of a space holder technique, in which NH₄HCO₃ is adopted to achieve a porous structure. The highly porous TNZTF alloy possesses a homogeneous fine–grained microstructure consisting of equiaxed α–Ti and a small amount of FeTi_2, the latter of which is distributed in the β–Ti matrix. Through adjusting the mass fraction of NH₄HCO₃, a novel high–porosity, and high–strength TNZTF alloy with a low modulus was successfully prepared. The porous alloy with the addition of 30 wt.% NH₄HCO₃ exhibits a porosity of 50.3 ± 0.2%, a maximum strength of 327.3 ± 2.1 MPa, and an elastic modulus of 12.2 ± 0.3 GPa. The strength enhancement is mainly attributed to the unique fine–grained microstructure, which is obtained by the crystallization of the amorphous phase and the ductile–brittle mixed fracture mechanism. The prepared porous TNZTF alloy possesses higher mechanical strength and well–matched elastic modulus, showing great potential as an implant material. Full article

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16 pages, 15654 KiB

Open AccessArticle

Influence of Single- and Double-Aging Treatments on the Mechanical and Corrosion Resistance of Alloy 625

by Barbara Rivolta, Riccardo Gerosa and Davide Panzeri

Metals 2024, 14(7), 823; https://doi.org/10.3390/met14070823 - 17 Jul 2024

Viewed by 607

Abstract

Nickel–chromium–molybdenum Alloy 625 exhibits an excellent combination of mechanical properties and corrosion resistance. However, the high-temperature plastic deformation process and the heat treatment represent critical aspects for the loss in mechanical strength by grain coarsening. This detrimental behavior is worsened by the absence [...] Read more.

Nickel–chromium–molybdenum Alloy 625 exhibits an excellent combination of mechanical properties and corrosion resistance. However, the high-temperature plastic deformation process and the heat treatment represent critical aspects for the loss in mechanical strength by grain coarsening. This detrimental behavior is worsened by the absence of phase transformation temperatures. However, the chemical composition permits slow precipitation-hardening response upon single aging. Therefore, when the soft- or solution-annealed condition is associated with insufficient mechanical properties, this potentiality can be exploited to improve the mechanical strength. Since the

γ^{″}

precipitation can be accelerated by double-aging treatment, different time–temperature combinations of double aging at 732 °C and 621 °C are investigated. The simultaneous precipitation of intergranular carbides can dramatically affect the corrosion resistance. Such an undesired phenomenon occurs very quickly at 732 °C, but it is obtained only after very long exposure times at 621 °C. For this reason, a performance chart is developed to compare all the tested conditions. In particular, single aging at 621 °C for 72 h and 130 h are associated with an acceptable combination of mechanical and corrosion properties. Double aging permits a conspicuous acceleration of the aging response. For instance, with double aging at 732 °C 3 h and 621 °C 72 h, it is possible to obtain the same mechanical properties of single aging at 621 °C for 260 h. Such acceleration is accompanied by a more critical corrosion behavior, especially because of the primary step. However, even after its optimization, none of the tested conditions were acceptable. Full article

(This article belongs to the Special Issue Characterization and Processing Technology of Superalloys)

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16 pages, 17372 KiB

Open AccessArticle

Parameter Equivalence and Impedance Characteristics of NiTi Wires Embedded in Nitrile Butadiene Rubber Based on Secondary Bridging Model

by Yizhe Huang, Xipeng Luo, Huizhen Zhang, Jun Wang, Bin Huang, Zhifu Zhang, Qibai Huang and Xin Zhan

Metals 2024, 14(7), 822; https://doi.org/10.3390/met14070822 - 17 Jul 2024

Viewed by 589

Abstract

This article presents a metal matrix composite material consisting of NiTi wires embedded in nitrile butadiene rubber (NBR) that preserves NBR’s inherent acoustic characteristics while enabling acoustic modification through the NiTi phase transition induced by stress and temperature. The macroscopic mechanical parameters of [...] Read more.

This article presents a metal matrix composite material consisting of NiTi wires embedded in nitrile butadiene rubber (NBR) that preserves NBR’s inherent acoustic characteristics while enabling acoustic modification through the NiTi phase transition induced by stress and temperature. The macroscopic mechanical parameters of transversely isotropic NiTi-NBR composite materials are derived by means of a secondary bridging model that takes into account interfacial phases. On this basis, the acoustic impedance properties and absorption coefficient of composite materials were examined as a function of NiTi volume fraction using the transfer matrix method. The accuracy and effectiveness of the theoretical method were verified by comparing the calculated results with finite element simulation. The research results indicated that regulating the volume fraction of NiTi can lead to the anticipated value of the input impedance of composite materials, improving impedance matching with media like water and rubber, which offers novel insights and a theoretical foundation for the development of underwater sound-absorbing materials. Full article

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19 pages, 7301 KiB

Open AccessArticle

The Melting Behavior of Hydrogen Direct Reduced Iron in Molten Steel and Slag: An Integrated Computational and Experimental Study

by Fabian Andres Calderon Hurtado, Joseph Govro, Arezoo Emdadi and Ronald J. O’Malley

Metals 2024, 14(7), 821; https://doi.org/10.3390/met14070821 - 17 Jul 2024

Cited by 1 | Viewed by 805

Abstract

Direct reduced iron (DRI) and hot briquetted iron (HBI) are essential feedstocks for tramp element control in the electric arc furnace (EAF). Due to greenhouse gas (GHG) concerns related to CO₂ emissions, hydrogen as a substitute for natural gas and a reductant [...] Read more.

Direct reduced iron (DRI) and hot briquetted iron (HBI) are essential feedstocks for tramp element control in the electric arc furnace (EAF). Due to greenhouse gas (GHG) concerns related to CO₂ emissions, hydrogen as a substitute for natural gas and a reductant in DRI production is being widely explored to reduce GHG emissions in ironmaking. This study examines the melting behavior of hydrogen DRI (H-DRI) pellets in the EAF containing low-carbon (0.1 wt.%) molten steel and molten slag. A computational heat transfer model was developed to predict the melting behavior of H-DRI pellets. To validate the model, a set of experimental laboratory simulations was conducted by immersing H-DRI in a molten steel bath and slag. The temperature history at the center of the pellet during melting and the shell thickness at different melting stages were utilized to validate the model. The simulation results agree with the experimental measurements of steel balls and H-DRI in different metallic molten steel and slag baths. Full article

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13 pages, 1889 KiB

Open AccessArticle

The Effect of Germanium Additions on the Mechanical Properties of Zn-Mg-Al Alloys

by Amar Dhoj Malla, James Henley Sullivan, David Jonathan Penney, Elizabeth Sackett, Robert Joseph Lancaster and Peter Barker

Metals 2024, 14(7), 820; https://doi.org/10.3390/met14070820 - 16 Jul 2024

Viewed by 788

Abstract

In this investigation, 0.19–1.8 wt.% of Ge was introduced into a ternary Zn-Mg-Al alloy. The introduction of Ge had a significant impact on the microstructure, leading to the formation of Mg₂Ge. The area fraction of the eutectic phase diminished with increasing [...] Read more.

In this investigation, 0.19–1.8 wt.% of Ge was introduced into a ternary Zn-Mg-Al alloy. The introduction of Ge had a significant impact on the microstructure, leading to the formation of Mg₂Ge. The area fraction of the eutectic phase diminished with increasing Ge additions. Small-scale test techniques were utilised to evaluate the mechanical properties due to the changes in microstructure. Zn-Mg-Al alloys were found to be inherently harder compared to standard hot-dip Zn-containing 0.2 wt.% Al. The hardness and strength of the Zn-Mg-Al alloys decreased with the increase in Ge additions. Full article

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13 pages, 1714 KiB

Open AccessArticle

Optimization of Billet Cooling after Continuous Casting Using Genetic Programming—Industrial Study

by Miha Kovačič, Aljaž Zupanc, Robert Vertnik and Uroš Župerl

Metals 2024, 14(7), 819; https://doi.org/10.3390/met14070819 - 16 Jul 2024

Viewed by 649

Abstract

ŠTORE STEEL Ltd. is one of the three steel plants in Slovenia. Continuous cast 180 mm × 180 mm billets can undergo cooling to room temperature using a turnover cooling bed. They can also be cooled down under hoods or heat treated to [...] Read more.

ŠTORE STEEL Ltd. is one of the three steel plants in Slovenia. Continuous cast 180 mm × 180 mm billets can undergo cooling to room temperature using a turnover cooling bed. They can also be cooled down under hoods or heat treated to reduce residual stresses. Additional operations of heat treatment from 36 h up to 72 h and cooling of the billets for 24 h, with limited capacities (with only two heat treatment furnaces and only six hoods), drastically influence productivity. Accordingly, the casting must be carefully planned (i.e., the main thing is casting in sequences), while the internal quality of the billets (i.e., the occurrence of inner defects) may be compromised. Also, the stock of billets can increase dramatically. As a result, it was necessary to consider the abandoning of cooling under hoods and heat treatment of billets. Based on the collected scrap data after ultrasonic examination of rolled bars, linear regression and genetic programming were used for prediction of the occurrence of inner defects. Based on modeling results, cooling under hoods and heat treatment of billets were abandoned at the casting of several steel grades. Accordingly, the casting sequences increased, and the stock of billets decreased drastically while the internal quality of the rolled bars remained the same. Full article

(This article belongs to the Special Issue Computational Methods in Metallic Materials Manufacturing Processes)

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16 pages, 15862 KiB

Open AccessArticle

Pulsed Magnetic Field Treatment Effects on Undissolved Carbides in Continuous Casting Billets of GCr15 Bearing Steel

by Lijuan Shen, Ruiqing Lang, Shuqing Xing and Yonglin Ma

Metals 2024, 14(7), 818; https://doi.org/10.3390/met14070818 - 16 Jul 2024

Viewed by 616

Abstract

The study investigates the effect of pulsed magnetic fields on undissolved carbides in high-carbon chromium bearing steel GCr15 billets. The billets were subjected to heat treatment at 950 °C, with a pulsed magnetic field of varying durations applied during the process. The influence [...] Read more.

The study investigates the effect of pulsed magnetic fields on undissolved carbides in high-carbon chromium bearing steel GCr15 billets. The billets were subjected to heat treatment at 950 °C, with a pulsed magnetic field of varying durations applied during the process. The influence of the pulsed magnetic field on the distribution of undissolved carbides within the billets was investigated, and the thermodynamic and kinetic mechanisms of undissolved carbides dissolution were explored. The results indicate that the area percentage of undissolved carbides in the microstructure decreases from 1.68% to 0.06% after applying a pulsed magnetic field for 10 min, and the size of undissolved carbides decreases from 17.5 μm to 4.9 μm. When a pulsed magnetic field is applied for 30 min, all undissolved carbides dissolve. The statistics demonstrate that the average size of undissolved carbides is reduced from 14.19 μm to 0.63 μm, with a reduction percentage reaching 96%. Over the same duration, the number density of the undissolved carbides decreases from (0.19~0.55)/mm² to (0.03~0.1)/mm², and the percentage area of the undissolved carbides decreases from (1.26~1.68)% to (0~0.02)%. Thermodynamically, applying a pulsed magnetic field lowers the dissolution energy barrier of undissolved carbides and modifies their transformation temperature. Kinetically, the rate of alloy element diffusion is enhanced by increasing the frequency of atomic jumps. This research aims to provide new insights into enhancing the contact fatigue life of bearing steel, increasing the proportion of special steel, and optimizing the steel deep-processing process. Full article

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18 pages, 4417 KiB

Open AccessArticle

Obtention of Suitable Pregnant Leach Solution (PLS) for Copper Solvent Extraction Plants from Copper Concentrate Using Hydrogen Peroxide and Iodine in a Sulfuric Acid–Chloride Medium

by María E. Taboada, Nathalie E. Jamett, German A. Moraga, Pia C. Hernández and Teófilo A. Graber

Metals 2024, 14(7), 817; https://doi.org/10.3390/met14070817 - 16 Jul 2024

Viewed by 766

Abstract

Copper leaching presents an environmentally friendly alternative to traditional sulfide ore processing methods. This study investigates an efficient leaching process for copper concentrate, utilizing a solution of sulfuric acid (H₂SO₄) and potassium iodide (KI) in a chloride medium (NaCl), [...] Read more.

Copper leaching presents an environmentally friendly alternative to traditional sulfide ore processing methods. This study investigates an efficient leaching process for copper concentrate, utilizing a solution of sulfuric acid (H₂SO₄) and potassium iodide (KI) in a chloride medium (NaCl), enhanced by hydrogen peroxide (H₂O₂) at room temperature. A significant aspect of this research was optimizing the KI concentration to minimize iodide sublimation into iodine gas (I₂). Through the experimental design, the optimal dosages of reagents were determined, leading to maximized copper extraction of approximately 27% in 45 min of testing at room temperature. The results showed that it is possible to obtain a suitable pregnant leach solution (PLS) (i.e., in the range of 3 to 8 g/L of Cu) for treatment in available copper solvent extraction (SX) plants with a cost of less than 4.5 USD/t Cu, according to the economic analysis carried out. The results of this study determine the most effective operational conditions for leaching and ensure a suitable PLS for SX plants in a cost-effective and environmentally friendly manner. This approach could significantly contribute to more sustainable practices in the mining and processing of copper ores. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Hydrometallurgy—2nd Edition)

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13 pages, 4573 KiB

Open AccessArticle

Influence of CAD/CAM Manufacturing Technique and Implant Abutment Angulation on Loosening of Individual Screw-Retained Implant Crowns

by Aitana Rico-Coderch, Luis F. Félix, María Fernanda Solá-Ruiz, Michell Medina, Rubén Agustín-Panadero, Rocío Ortega, Rocío Cascos and Miguel Gómez-Polo

Metals 2024, 14(7), 816; https://doi.org/10.3390/met14070816 - 15 Jul 2024

Viewed by 735

Abstract

Background: Dental implant abutment screw loosening is an increasingly common problem, as evidenced by multiple studies that have investigated its causes. The objective of this study was to compare the screw loosening torque values before and after cyclic loading and to determine whether [...] Read more.

Background: Dental implant abutment screw loosening is an increasingly common problem, as evidenced by multiple studies that have investigated its causes. The objective of this study was to compare the screw loosening torque values before and after cyclic loading and to determine whether they are affected by the CAD/CAM abutment manufacturing technique (machined or laser-sintered) and abutment angulation. Materials and Methods: Ninety implants were used and divided into two groups: 45 implants received machined abutments (group A) and 45 implants received laser-sintered abutments (group B). Each group was further divided into three subgroups, with 15 implants each, based on the abutment angulation involved (0°, 15° and 20°). The abutments were tightened to the torque recommended by the manufacturer, and the reverse torque value was measured before and after cyclic loading (300,000 cycles). Data analysis was performed using one-way ANOVA and Wilcoxon signed-rank tests. Results: Statistically significant differences were observed between the laser-sintered and machined groups (p < 0.01). Additionally, differences were observed between subgroups with different angulations for both machined (16.2 ± 1.75, 14.7 ± 1.74 and 13.4 ± 1.08 Ncm) and laser-sintered abutments (14.6 ± 1.25, 12.7 ± 1.2 and 11.1 ± 1.35 Ncm) (0°, 15° and 20°, respectively). Conclusions: The final screw loosening torque after cyclic loading was lower than the initial loosening torque. Both abutment angulation and the CAD/CAM manufacturing method exerted a statistically significant influence on the final loosening torque. The abutment angulation factor was estimated to have an influence of 34.5%, while the abutment manufacturing method was estimated to have an influence of 21%. Full article

(This article belongs to the Special Issue Recent Advances in Metallic Biomaterials)

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19 pages, 9281 KiB

Open AccessArticle

A Study on the Optimal Powder Metallurgy Process to Obtain Suitable Material Properties of Soft Magnetic Composite Materials for Electric Vehicles

by Seongsu Kang and Seonbong Lee

Metals 2024, 14(7), 815; https://doi.org/10.3390/met14070815 - 15 Jul 2024

Viewed by 737

Abstract

This study systematically investigates the impact of the material properties of soft magnetic composites (SMCs) on the powder metallurgy forming process. It proposes a suitable material selection process for various motor types and shapes and determines the optimal forming conditions for each SMC [...] Read more.

This study systematically investigates the impact of the material properties of soft magnetic composites (SMCs) on the powder metallurgy forming process. It proposes a suitable material selection process for various motor types and shapes and determines the optimal forming conditions for each SMC material. This study employed the Taguchi design method to identify key control factors such as powder type, forming temperature, and forming speed, and analyzed their effects on relative density. Simulation results indicated that AncorLam HR exhibited superior properties compared with AncorLam and Fe-6.5wt.%Si. The optimal conditions determined through signal-to-noise ratio (SNR) calculations were AncorLam HR at 60 °C and five cycles per minute (CPMs). Validation through simulation and SEM analysis confirmed improved density uniformity and reduced defects in products formed under optimal conditions. Final prototype testing demonstrated that the selected conditions achieved the target density with minimal variance, enhancing the mechanical properties and performance of the motors. These results suggest that the appropriate application of SMC materials can significantly enhance motor efficiency and reliability. Full article

(This article belongs to the Special Issue Soft Magnetic Composites: Manufacture, Properties and Applications)

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18 pages, 4533 KiB

Open AccessArticle

An Alternative Method of Investigating the Thermal Stability of Shoe-Braked Railway Wheel Steels Based on Strain Hardening Analysis

by Giuliano Angella, Lorenzo Ghidini and Michela Faccoli

Metals 2024, 14(7), 814; https://doi.org/10.3390/met14070814 - 14 Jul 2024

Viewed by 526

Abstract

During service, shoe-braked railway wheel steels are often subjected to a severe thermal cycle. Therefore, understanding the evolution of the microstructure and the resulting changes in mechanical properties during service is fundamental in the choice of steel. In previous research, the effects of [...] Read more.

During service, shoe-braked railway wheel steels are often subjected to a severe thermal cycle. Therefore, understanding the evolution of the microstructure and the resulting changes in mechanical properties during service is fundamental in the choice of steel. In previous research, the effects of the thermal loading on the microstructure and mechanical properties of five different steels for railway wheels (ER7, HYPERLOS^®, Class B, SANDLOS^® and Class C) were investigated by hardness, tensile and toughness tests, in the as-supplied condition and after different heat treatments designed to replicate the modification of the microstructure due to braking. In this paper, the tensile work hardening behavior was studied by interpolating the tensile flow curves with the constitutive equation related to the dislocation density proposed by Voce, which correlates the Voce equation parameters with the microstructural features of metallic materials. The work hardening analysis revealed that there is a good correlation between the Voce parameters and the microstructure of the five steels in as-supplied condition and after heat treatments. An interesting correlation was found between Voce parameters and apparent fracture toughness. After heat treatments at 700 °C and 750 °C the properties of the steels decreased, which was consistent with the evolution of the microstructure. However, after exposure at 970 °C with subsequent cooling in air, Class C steel appears to have a microstructure similar to the original microstructure, with tensile and toughness properties very similar to the as-supplied condition, demonstrating better microstructural stability compared to steels ER7, HYPERLOS^®, Class B and SANDLOS^®. Full article

(This article belongs to the Special Issue Design, Preparation and Properties of High Performance Steels)

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Graphical abstract

13 pages, 5842 KiB

Open AccessCommunication

A Comparative Analysis of a Microstructure and Properties for Monel K500 Hot-Rolled to a Round Bar and Wire Deposited on a Round Surface

by Andrii Kostryzhev, Olexandra Marenych, Zengxi Pan, Huijun Li and Stephen van Duin

Metals 2024, 14(7), 813; https://doi.org/10.3390/met14070813 - 13 Jul 2024

Viewed by 688

Abstract

Metal manufacturing processes based on deformation (forging, rolling) result in a fine grain structure with a complex dislocation substructure, which positively influence mechanical properties. Casting and additive manufacturing (powder- or wire-based) usually produce a coarse grain structure with a poorly developed dislocation substructure, [...] Read more.

Metal manufacturing processes based on deformation (forging, rolling) result in a fine grain structure with a complex dislocation substructure, which positively influence mechanical properties. Casting and additive manufacturing (powder- or wire-based) usually produce a coarse grain structure with a poorly developed dislocation substructure, which negatively affect mechanical properties. Heat treatment may alter phase balance and stimulate precipitation strengthening; however, precipitation kinetics depends on the dislocation substructure. In this paper, a comparative study of the microstructure and strength is presented for Monel K500 alloy containing 63 Ni, 30 Cu, 2.0 Mn, and 2.0 Fe (wt.%), and microalloyed with Al, Ti, and C hot-rolled to a round bar and deposited on a round surface using wire additive manufacturing (WAAM) technology. An increased dislocation density and number density of fine precipitates resulted in 8–25% higher hardness and 1.8–2.6 times higher compression yield stress in the hot-rolled alloy compared to these in the WAAM-produced alloy. However, due to a high work hardening rate, only 3–10% cold deformation was necessary to increase the strength of the WAAM alloy to this of the hot-rolled one. Age hardening heat treatment, through the intensification of the precipitation strengthening mechanism, reduced the value of cold deformation strain required to equalise the properties. Based on the obtained results, a new technology consisting of additive manufacturing, heat treatment, and cold deformation can be proposed. It can produce WAAM components with strength and hardness improved to the level of hot-rolled components, which is a significant development of additive manufacturing. Full article

(This article belongs to the Section Additive Manufacturing)

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20 pages, 16297 KiB

Open AccessArticle

Study on the Influence of Surface Roughness and Temperature on the Interface Void Closure and Microstructure Evolution of Stainless Steel Diffusion Bonding Joints

by Yanni Wei, Shuyuan Zhang, Lei Jia, Quanning Li and Mengfan Ma

Metals 2024, 14(7), 812; https://doi.org/10.3390/met14070812 - 12 Jul 2024

Viewed by 615

Abstract

Austenitic stainless steel diffusion bonding was performed, and the effects of the surface roughness and bonding temperature on the interface microstructure and mechanism of hole closure were investigated. The bonded interface microstructure was analyzed. The influence of surface roughness and temperature on cavity [...] Read more.

Austenitic stainless steel diffusion bonding was performed, and the effects of the surface roughness and bonding temperature on the interface microstructure and mechanism of hole closure were investigated. The bonded interface microstructure was analyzed. The influence of surface roughness and temperature on cavity evolution, bonding rate, and axial deformation rate was studied. The mechanism of interfacial void closure in the stainless steel diffusion bonding process was revealed. With the increase in temperature and the decrease in surface roughness, the size of the interface void and the bonded area decreased. The bonding rate can reach more than 95% when the surface roughness value is 0.045 μm and the temperature is at or higher than 750 °C. The analytical equations of interfacial bonding rate δ and axial deformation rate ε produced by the deformation mechanism were established, and the laws of the deformation mechanism and diffusion mechanism within interfacial hole closure were obtained. Full article

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15 pages, 3709 KiB

Open AccessArticle

Modeling and Research on the Defects of Pressed Rigging in a Geomagnetic Field Based on Finite Element Simulation

by Gang Zhao, Changyu Han, Zhongxiang Yu, Hongmei Zhang, Dadong Zhao, Guoao Yu and Zhengyi Jiang

Metals 2024, 14(7), 811; https://doi.org/10.3390/met14070811 - 12 Jul 2024

Viewed by 544

Abstract

It is very important to carry out effective safety inspections on suppression rigging because of the bad service environment of suppression rigging: marine environments. In this paper, the multi-parameter simulation method in ANSYS and ANSYS Electronics Suite simulation software is used to simulate [...] Read more.

It is very important to carry out effective safety inspections on suppression rigging because of the bad service environment of suppression rigging: marine environments. In this paper, the multi-parameter simulation method in ANSYS and ANSYS Electronics Suite simulation software is used to simulate the effect of geomagnetic fields on the magnetic induction intensity of defective pressed rigging under the variable stress in marine environments. The results of the ANSYS simulation and geomagnetic flaw detection equipment are verified. The simulation results show that, according to the multi-parameter simulation results of ANSYS and ANSYS Electronics Suite simulation software, it can be found that, under the action of transverse force, the internal stress of the pressed rigging will affect the magnetic field around pressed rigging with defects. With an increase in internal stress in the range of 0~20 MPa, the magnetic induction intensity increases to 0.55 A/m, and with an increase in internal stress in the range of 20~150 MPa, the magnetic induction intensity decreases to 0.06 A/m. From the use of a force magnetic coupling analysis method, it can be obtained, under the lateral force of the defects in suppressing rigging, that magnetic flux leakage signals decrease with an increase in the rigging’s radial distance. The experiment results show that the difference between the peak and trough of the magnetic induction intensity at the pressed rigging defect calculated by the ANSYS simulation is very consistent with the results measured by the geomagnetic flaw detection equipment. Full article

(This article belongs to the Special Issue Modeling Thermodynamic Systems and Optimizing Metallurgical Processes)

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14 pages, 7016 KiB

Open AccessArticle

Influence of Surface State on the Corrosion Behavior of Si-Reinforced F/M Steels under Solid-Phase Oxygen-Controlled Static Liquid LBE Environment

by Yuchen Liu, Bo Qin, Xiaogang Fu and Bin Long

Metals 2024, 14(7), 810; https://doi.org/10.3390/met14070810 - 11 Jul 2024

Viewed by 553

Abstract

Since F/M steel is one of the leading candidate materials for the lead-cooled fast reactor (LFR), its compatibility with the liquid LBE environment is an essential issue before application. One major way to improve LBE corrosion resistance is to control the oxygen concertation [...] Read more.

Since F/M steel is one of the leading candidate materials for the lead-cooled fast reactor (LFR), its compatibility with the liquid LBE environment is an essential issue before application. One major way to improve LBE corrosion resistance is to control the oxygen concertation in liquid LBE for the growth of a stable, protective oxide layer on the surface of the structure material. However, the influence of the surface state on corrosion behavior is a more realistic issue when it comes to practical applications. In this study, the corrosion behavior of Si-reinforced 9Cr and 11Cr F/M steels with different surface states was investigated by a static liquid LBE corrosion test under solid-phase oxygen-controlled conditions. The result showed that at 550 °C, the coarse surface state caused dissolution behavior at the initial stage of corrosion, while the fine surface state formed the oxide layer. Moreover, at 610 °C, Si-reinforced 11Cr F/M steel shows better liquid LBE corrosion resistance due to its thinner oxide layer formation. Full article

(This article belongs to the Section Corrosion and Protection)

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22 pages, 15916 KiB

Open AccessArticle

Inconel 740H Prepared by Additive Manufacturing: Microstructure and Mechanical Properties

by Ruizhang Hu, Wenqing Li, Chun Guo, Guangcan Huang, Xinyu Zhang and Qingcheng Lin

Metals 2024, 14(7), 809; https://doi.org/10.3390/met14070809 - 11 Jul 2024

Viewed by 621

Abstract

An Inconel 740H nickel-based alloy was fabricated via wire arc additive manufacturing. The as-welded and heat-treated samples were analyzed to investigate their phase composition, microstructure, crystal structure, and mechanical properties. After heat treatment, the sample exhibited a columnar crystal zone microstructure consisting of [...] Read more.

An Inconel 740H nickel-based alloy was fabricated via wire arc additive manufacturing. The as-welded and heat-treated samples were analyzed to investigate their phase composition, microstructure, crystal structure, and mechanical properties. After heat treatment, the sample exhibited a columnar crystal zone microstructure consisting of a γ matrix + precipitated phase, the remelting zone metallographic structure was a γ matrix + precipitated phase, and the HAZ metallographic structure was a γ matrix + precipitated phase. Transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were used to show that the welded sample exhibited many dislocations, a few inclusions, and carbides, nitrides, and γ’ precipitates in its crystal structure. In contrast, the crystal structure of the heat-treated sample exhibited a lower number of dislocations and significantly higher carbide and γ’ precipitate content. Moreover, the mechanical performance of these samples was excellent. This heat-treatment process improved the sample strength by about 200 MPa, leading to better high-temperature mechanical properties. This work is anticipated to offer theoretical and experimental support for using additive manufacturing methods in the manufacturing of nickel-based superalloy components. Full article

(This article belongs to the Section Additive Manufacturing)

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