Metals

19 pages, 14998 KiB

Open AccessArticle

Notch Fatigue Damage Evolution Mechanism of TC21 Alloy with Multilevel Lamellar Microstructures

by Xiaosong Zhou, Xiang Li, Chaowen Huang, Quan Wu and Fei Zhao

Metals 2025, 15(1), 18; https://doi.org/10.3390/met15010018 (registering DOI) - 29 Dec 2024

Abstract

This study aims to explore the effect of microstructural parameters on the notch fatigue damage behavior of the TC21 alloy. Different levels of lamellar microstructures were achieved through distinct aging temperatures of 550 °C, 600 °C, and 650 °C. The findings reveal that [...] Read more.

This study aims to explore the effect of microstructural parameters on the notch fatigue damage behavior of the TC21 alloy. Different levels of lamellar microstructures were achieved through distinct aging temperatures of 550 °C, 600 °C, and 650 °C. The findings reveal that increasing aging temperature primarily contributes to the augmentation of α colony (α_c) thickness, grain boundaries α phase (GBα) thickness, and α fine (α_fine) size alongside a reduction in α lath (α_lath) thickness and α_fine content. The notch alters stress distribution and relaxation effects at the root, enhancing notched tensile strength while weakening plasticity. Moreover, the increased thickness of GBα emerges as a critical factor leading to the increase area of intergranular cleavage fracture. It is noteworthy that more thickness α_lath and smaller α_fine facilitate deformation coordination and enhance dislocation accumulation at the interface, leading to a higher propensity for micro-voids and micro-cracks to propagate along the interface. Conversely, at elevated aging temperatures, thinner α_lath and larger α_fine are more susceptible to fracture, resulting in the liberation of dislocations at the interface. The reduction in α_lath thickness is crucial for triggering the initiation of multi-system dislocations at the interface, which promotes the development of persistent slip bands (PSBs) and dislocation nets within α_lath. This phenomenon induces inhomogeneous plastic deformation and localized hardening, fostering the formation of micro-voids and micro-cracks. Full article

(This article belongs to the Special Issue Structure and Mechanical Properties of Titanium Alloys)

16 pages, 3424 KiB

Open AccessArticle

Efficient Modeling Framework for FO-WLP Solder Interconnect Behavior During Thermal Cycling

by Ramiro Sebastian Vargas Cruz and Viktor Gonda

Metals 2025, 15(1), 17; https://doi.org/10.3390/met15010017 (registering DOI) - 29 Dec 2024

Abstract

In advanced microelectronic packaging, high thermo-mechanical loads arise on the solder interconnects. Accurate and efficient modeling of the mechanical behavior is crucial in the design of the package, and the simulation results can provide a basis for estimations of the reliability of the [...] Read more.

In advanced microelectronic packaging, high thermo-mechanical loads arise on the solder interconnects. Accurate and efficient modeling of the mechanical behavior is crucial in the design of the package, and the simulation results can provide a basis for estimations of the reliability of the assembly. However, the accuracy of the simulation results depends on the accuracy of the modeled geometry and the modeling simplifications and assumptions employed to achieve computational cost-efficient calculations. In this work, finite element analysis (FEA) of a Fan Out—Wafer Level Packaging (FO-WLP) layout was carried out considering the following variations: modeling domain (2-D and pseudo-3-D) was defined for creating the efficient calculation framework, where soldering material (SAC 305 and SACQ), incorporation of intermetallic compound (IMC), bond pad edge geometry (sharp and blunt) were modeled for cycles of thermal load. Stress and strain analysis was carried out to evaluate the solder behavior for the parameter variations. Furthermore, fatigue indicators were evaluated. An efficient planar simulation framework with 2-D and pseudo-3-D meshed geometries provides a quick estimate for the lower and upper bound for the strain, stress and strain energy-related parameters, respectively. This calculation framework can be employed for extensive parameter studies solved rapidly at low computational costs. Full article

(This article belongs to the Special Issue Advanced Studies in Solder Joints)

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14 pages, 6900 KiB

Open AccessArticle

Interfacial Microstructure and Cladding Corrosion Resistance of Stainless Steel/Carbon Steel Clad Plates at Different Rolling Reduction Ratios

by Jie Chen, Yixin Zhu, Xia Chen, Xiaoli Ma and Bin Chen

Metals 2025, 15(1), 16; https://doi.org/10.3390/met15010016 (registering DOI) - 28 Dec 2024

Abstract

Optical microscope (OM), energy dispersive spectrometer (EDS), electron backscatter diffractometer (EBSD), electrochemical test, and transmission electron microscope (TEM) were employed to conduct interface microstructure observation and cladding corrosion resistance analysis on 304 SS/CS clad plates that have four different reduction ratios. The increase [...] Read more.

Optical microscope (OM), energy dispersive spectrometer (EDS), electron backscatter diffractometer (EBSD), electrochemical test, and transmission electron microscope (TEM) were employed to conduct interface microstructure observation and cladding corrosion resistance analysis on 304 SS/CS clad plates that have four different reduction ratios. The increase in rolling reduction ratio leads to larger grain size, gradually refined microstructure, and a decreased thickness of the interfacial martensite area. As the concentration disparity of the C element between carbon steel (CS) and 304 stainless steel (SS) is small, no evident carburization layer or decarburization layer can be detected. The ferrite microstructure on the CS side has greater stress distribution and greater local orientation deviation, and deformed grains are dominant. Austenite undergoes strain-induced martensitic transformation with the transformation mechanism of γ→twinning→a’-martensite. The martensite microstructure within the interface region grows in the direction of the interior of austenite grains. The reduction ratio increases sharply, leading to an increase in dislocation density, which promotes the nucleation, growth, and precipitation of carbides and seriously reduces the corrosion resistance of the cladding. Subsequently, the reduction ratio keeps on increasing. However, the degree of change in the reduction ratio diminishes. High temperature promotes the dissolution of carbides and improves the corrosion resistance. From this, it can be understood that by applying the process conditions of raising the reduction ratio and keeping a high temperature at the carbide dissolution temperature, a clad plate that has excellent interface bonding and remarkable corrosion resistance can be acquired. Full article

(This article belongs to the Special Issue Numerical Simulation and Experimental Research of Metal Rolling)

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16 pages, 7792 KiB

Open AccessArticle

The Influence Mechanism of Deformation on the Precipitation Behavior and Mechanical Properties of 7075 Aluminum Alloy During Hot Forming-Quenching Integrated Process

by Huanhuan Li, Xinhang Zhang, Wei Dai, Wei Yan, Chaomei He, Jiake Luo, Mengxing Li, Ruolin Wu and Dang Wang

Metals 2025, 15(1), 15; https://doi.org/10.3390/met15010015 (registering DOI) - 28 Dec 2024

Abstract

The hot forming-quenching integrated process (HFQ^®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ^® has a non-negligible influence on precipitation [...] Read more.

The hot forming-quenching integrated process (HFQ^®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ^® has a non-negligible influence on precipitation behavior in subsequent artificial aging treatment and affects the mechanical properties of the formed parts. In this study, the relationship between the precipitation behavior and thermal deformation ratios was investigated. Results indicated that the formation temperatures of η′ and η decreased with an increasing deformation ratio; however, the former decreased more than the latter. The activation energy of η′ precipitation decreased linearly with increasing deformation ratio. Additionally, the phase transition fraction of η′ increased with the deformation ratio, leading to shorter times required to reach equivalent phase transition fractions. Deformation accelerated the phase transition of η′, and greater deformation resulted in a shorter transition time. The aging time required for peak Vickers hardness decreased with increasing deformation ratio, reflecting the promotion of precipitated phase formation and transformation by introduced dislocations. Consequently, peak hardness and yield strength were achieved in shorter aging times. In terms of industrial applications, this discovery offers significant advantages for shortening the production cycle of the hot stamping process and reducing production costs. Full article

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19 pages, 8007 KiB

Open AccessArticle

Study on Near-Net Shape Forging of Large Marine Crank Throws

by Longjiang Niu, Qingliang Zhang, Yongwan Zhang, Jingyu Wang, Weiping Luo, Donghang Liu, Tengfei Ma and Xavier Velay

Metals 2025, 15(1), 14; https://doi.org/10.3390/met15010014 (registering DOI) - 28 Dec 2024

Abstract

The crankshaft is a critical component in large marine ships, often regarded as the “heart” of the vessel due to its role in transmitting power and motion. This article addresses the technological challenges in the forging of marine crank throws, a key segment [...] Read more.

The crankshaft is a critical component in large marine ships, often regarded as the “heart” of the vessel due to its role in transmitting power and motion. This article addresses the technological challenges in the forging of marine crank throws, a key segment of the crankshaft. The study employed finite element simulations to evaluate three Near-Net-Shape (NNS) forming methods: One-Step Extrusion (OSE), Upsetting/Backward Extrusion (U/BE), and Grooving–upsetting/Backward Extrusion (G–U/BE). The results show that the G–U/BE method requires the lowest load. The grooving–upsetting step in the G–U/BE process forms a rigid journal end web shape that influences the subsequent backward extrusion, with the relative groove depth (the ratio of groove depth to width) playing a crucial role in the final forging quality. Optimal crank throw formation occurs when the ratio is 1.5; deeper grooves increase the load required, diminishing the effectiveness of the grooving–upsetting step. Scaled-down experiments validate G–U/BE as a practical and feasible method for producing large marine crank throw forgings, ensuring both the desired shape and microstructural properties. Full article

(This article belongs to the Special Issue Advanced Plastic Forming Processes: Theory, Experiments and Numerical Simulations)

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14 pages, 2603 KiB

Open AccessArticle

Feature Engineering to Embed Process Knowledge: Analyzing the Energy Efficiency of Electric Arc Furnace Steelmaking

by Quantum Zhuo, Mansour N. Al-Harbi and Petrus C. Pistorius

Metals 2025, 15(1), 13; https://doi.org/10.3390/met15010013 (registering DOI) - 28 Dec 2024

Abstract

The importance of electric arc furnace (EAF) steelmaking is expected to increase worldwide as parts of the industry transition to lower carbon dioxide emissions. This work analyzed one year’s operational data from an EAF plant that uses a large proportion of direct-reduced iron [...] Read more.

The importance of electric arc furnace (EAF) steelmaking is expected to increase worldwide as parts of the industry transition to lower carbon dioxide emissions. This work analyzed one year’s operational data from an EAF plant that uses a large proportion of direct-reduced iron (DRI) in the furnace feed. The data were used to test different approaches to quantifying the effects of process conditions on specific electricity consumption (kWh per ton of crude steel). In previous work, inputs such as the proportion of DRI, fluxes, natural gas, and oxygen were linearly correlated with the specific electricity consumption. The current work has confirmed that conventional multiple linear regression (MLR) reproduces electricity consumption trends in EAF steelmaking, but many model coefficients deviated significantly from expected values and appeared unphysical. The implementation of engineered features—the slag volume and total carbon input—in an MLR model resulted in coefficients that were closer to expectations, but did not improve prediction accuracy. Further improvement was obtained by applying the engineered features to a non-linear machine-learned model (based on XGBoost), yielding both physically reasonable trends and smaller prediction errors. Trends from Shapley dependence analysis (applied to the XGBoost model) are quantitatively consistent with theoretical trends. These include the energy needed to melt slag, and the endothermic effect of carbon additions. The fitted models demonstrate the potential to diagnose poor slag foaming by showing an increase in electricity consumption with increased oxygen use. This example demonstrates that practically important steelmaking process insights inferred via a linear regression approach can be improved by applying Shapley analysis to a machine-learned model based on engineered features. Full article

(This article belongs to the Special Issue Computational Methods in Metallic Materials Manufacturing Processes 2025)

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14 pages, 2447 KiB

Open AccessArticle

The Shear Bond Strength of Porcelain Bonding to Cobalt-Chromium Dental Alloys Before and After Thermal Cycling

by Ewa Pruszczyńska, Zofia Kula, Katarzyna Dąbrowska and Leszek Klimek

Metals 2025, 15(1), 12; https://doi.org/10.3390/met15010012 (registering DOI) - 28 Dec 2024

Abstract

Metal-ceramic crowns and bridges provide a stable and aesthetic tooth reconstruction. Hot pressing of veneering ceramics to metal substructure minimizes the formation of pores. Within the oral cavity, prosthetic structures are exposed to thermal stress. The study examines the influence of temperature changes [...] Read more.

Metal-ceramic crowns and bridges provide a stable and aesthetic tooth reconstruction. Hot pressing of veneering ceramics to metal substructure minimizes the formation of pores. Within the oral cavity, prosthetic structures are exposed to thermal stress. The study examines the influence of temperature changes on the quality and durability of the metal-ceramic bond using thermocyclic loading. Prior to the ceramic pressing, 40 cylindrical alloy specimens (height: 15 mm, diameter: 7 mm) were treated with abrasive blasting using Al₂O₃ (250 µm) or SiC (250 µm). They were divided into four groups: two control groups (sandblasted with Al₂O₃ or SiC) and two groups subjected to thermocyclic simulation. The ceramic-to-metal bond strength was measured with a shear test before and after thermocyclic loading. A statistically significant reduction in the bond strength between the metal substructure and the pressed ceramic was found after thermocyclic exposure. The bond strength decreased by 57% for Al₂O₃ sandblasted specimens and 36% for those sandblasted with SiC, as against the control group. This indicates that thermocycling weakens the bond between the metal alloy and pressed ceramic. The SiC blasting of the cobalt-chromium alloy results in a higher shear bond strength of the material connection after thermocyclic stimulation than the abrasive blasting with Al₂O₃. Full article

20 pages, 2304 KiB

Open AccessArticle

Computationally Effective Modeling of Cold Rolling: Application to Al Alloys

by János György Bátorfi and Jurij J. Sidor

Metals 2025, 15(1), 11; https://doi.org/10.3390/met15010011 (registering DOI) - 27 Dec 2024

Abstract

An accurate and numerically efficient description of the rolling process is a challenging task since the degree of computational accuracy is directly related to the complexity of the algorithm employed. In the most general case, finite element models (FEM) are used for the [...] Read more.

An accurate and numerically efficient description of the rolling process is a challenging task since the degree of computational accuracy is directly related to the complexity of the algorithm employed. In the most general case, finite element models (FEM) are used for the simulation of deformation processes; however, these techniques require significant computational time. Analytical approaches, which are suited for one or another deformation process, seem to be a proper alternative to FEM. In this study, the well-established flowline modeling approach (FLM) is extended with the aim of better describing the flow of a rolled material in both surface and subsurface regions. A new flowline function is defined, while the velocity along the particular streamline and strain rate gradients are determined analytically, based on the roll gap geometry. The new model is validated by comparing the velocity components to the ones computed by the finite element model. The distortion of meshes predicted by both FEM and FLM follow the same evolutionary pattern. Full article

(This article belongs to the Special Issue Numerical Simulation and Experimental Research of Metal Rolling)

17 pages, 1322 KiB

Open AccessArticle

Characteristics of Microstructure and Fracture Toughness According to the Groove Shape of Submerged Arc Welding

by Yong-Taek Shin, Chang-Ju Jung, Seong-Han Bae, Gyubaek An, Myungrak Son and Young-Il Park

Metals 2025, 15(1), 10; https://doi.org/10.3390/met15010010 (registering DOI) - 27 Dec 2024

Abstract

This study investigates the effects of heat input on the microstructure and fracture toughness of SAW (Submerged Arc Welding) joints with K-groove and X-groove weld preparations using S460NL steel. Microstructural analysis focused on acicular ferrite, grain boundary ferrite, and MA (Martensite–Austenite) constituents to [...] Read more.

This study investigates the effects of heat input on the microstructure and fracture toughness of SAW (Submerged Arc Welding) joints with K-groove and X-groove weld preparations using S460NL steel. Microstructural analysis focused on acicular ferrite, grain boundary ferrite, and MA (Martensite–Austenite) constituents to assess their influence on CTOD (Crack Tip Opening Displacement). The results indicate that the K-groove achieved a higher CTOD value of 0.82 mm compared to 0.13 mm for the X-groove, attributed to differences in microstructural composition and cooling rates. The findings highlight the impact of groove geometry and heat input on weld performance. Full article

(This article belongs to the Special Issue Fracture Mechanics of Metals (2nd Edition))

15 pages, 3445 KiB

Open AccessArticle

Temperature-Dependent Mechanical Properties of CoCrFeNi Medium-Entropy Alloy Produced by Laser-Directed Energy Deposition

by Margarita Klimova, Igor Krasanov, Ilya Astakhov, Ekaterina Kovalenko, Elizaveta Kochura, Anastasia Semenyuk, Sergey Zherebtsov, Olga Klimova-Korsmik and Nikita Stepanov

Metals 2025, 15(1), 9; https://doi.org/10.3390/met15010009 - 27 Dec 2024

Abstract

The temperature dependence of the mechanical properties of the CoCrFeNi medium-entropy alloy (MEA) manufactured by laser-directed energy deposition (L-DED) and additionally annealed at 1200 °C for 24 h was studied. The microstructure of the as-deposited alloy was represented by a single-phase face-centered cubic [...] Read more.

The temperature dependence of the mechanical properties of the CoCrFeNi medium-entropy alloy (MEA) manufactured by laser-directed energy deposition (L-DED) and additionally annealed at 1200 °C for 24 h was studied. The microstructure of the as-deposited alloy was represented by a single-phase face-centered cubic structure with coarse columnar grains and a high density of dislocation. Annealing resulted in the development of recrystallization and a reduction in dislocation density. The CoCrFeNi alloy produced by L-DED demonstrated mechanical properties comparable with those of the fine-grained equiatomic CoCrFeMnNi alloy, produced by casting followed by thermomechanical processing. Namely, as-deposited CoCrFeNi had a yield strength (YS) and ultimate tensile strength (UTS) of YS = 370 MPa and UTS = 610 MPa at room temperature, and YS = 565 MPa and UTS = 965 MPa at cryogenic temperature, along with a ductility of ~60%. Annealing resulted in a decrease in strength to YS = 180/350 MPa at 293/77 K. A quantitative analysis of various strengthening mechanisms showed that some strength increment of the as-deposited alloy was ensured by the high dislocation density formed during L-DED. Full article

16 pages, 5551 KiB

Open AccessArticle

Determination of Diffusion Coefficients of Nickel and Vanadium into Stainless and Duplex Steel and Titanium

by Šárka Vávrová, Martin Švec, Jaromír Moravec and Daniel Klápště

Metals 2025, 15(1), 8; https://doi.org/10.3390/met15010008 - 27 Dec 2024

Abstract

When heterogeneous joints are created, problems with the formation of intermetallic phases arise. There are various ways to reduce the formation of intermetallics. One of the ways that is discussed in this article is to use a suitable interlayer of appropriate thickness when [...] Read more.

When heterogeneous joints are created, problems with the formation of intermetallic phases arise. There are various ways to reduce the formation of intermetallics. One of the ways that is discussed in this article is to use a suitable interlayer of appropriate thickness when forming the joint. A too-thin interlayer does not protect against the formation of brittle intermetallic phases. On the other hand, a too-thick interlayer increases the heterogeneity of the joint and, thus, decreases its useful properties. Within this paper, the formation of diffusion joints between the base material (AISI 304 steel, duplex steel, AISI 316L steel, or titanium grade 2) and the 0.2 mm thick intermediate layer (nickel or vanadium) was studied. Initial diffusion joints were prepared in a Gleeble 3500 machine, and samples for the study of diffusion kinetics were subsequently heat-treated in a vacuum furnace. The result of the research was the determination of specific diffusion parameters of nickel and vanadium into all four tested base materials. The initial diffusion depth (simple heating to the target temperature without holding at this temperature) of nickel was 4.46 µm into duplex steel and 5.48 µm into Ti Gr. 2 at 950 °C. At the same temperature, the initial diffusion depth of vanadium was 14.54 µm into duplex steel and 14.32 µm into Ti Gr. 2. In addition, general equations for the calculation of diffusion coefficients for the mentioned materials in the temperature range of 850 to 1150 °C were established. Full article

(This article belongs to the Special Issue Brazing and Diffusion Welding of New Materials and Dissimilar Materials)

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17 pages, 6449 KiB

Open AccessArticle

Numerical Study on Combustion Behavior of Tuyere and Raceway in Blast Furnace with Oxygen-Rich Blast and Hydrogen Injection

by Ruimeng Shi, Yue Pei, Mengmeng Ren, Zheng Xue, Xinqi Li and Heping Liu

Metals 2025, 15(1), 7; https://doi.org/10.3390/met15010007 - 26 Dec 2024

Abstract

The injection of hydrogen into a blast furnace is a promising technology to fulfill the low-carbon ironmaking purpose. A three-dimensional computational fluid dynamic (CFD) model is developed to investigate the effect of hydrogen injection rate and blast oxygen enrichment rate on the tuyere, [...] Read more.

The injection of hydrogen into a blast furnace is a promising technology to fulfill the low-carbon ironmaking purpose. A three-dimensional computational fluid dynamic (CFD) model is developed to investigate the effect of hydrogen injection rate and blast oxygen enrichment rate on the tuyere, raceway, and surrounding coke bed behaviors. It was found that hydrogen injection leads to a higher water vapor volume fraction in the raceway and a higher hydrogen fraction in the coke bed. The magnitude of velocity and temperature near the tuyere only increase slightly due to the cold inlet temperature of hydrogen, which also results in lower coke bed temperature. The volume-averaged temperature decreases from 2146 K to 2129 K when the injection rate increases from 0 to 1000 Nm³/h. Oxygen enrichment rate presents a highly positive correlation with temperature in the raceway and coke bed, water vapor and carbon dioxide volume fraction in the raceway, and pulverized coal burnout rate. Because more carbon participates in the raceway reaction with an increase in oxygen enrichment rate from 0% to 10%, the final carbon monoxide fraction in the coke bed increases from 0.29 to 0.40, and the final hydrogen fraction decreases from 0.15 to 0.13. With the increase in hydrogen injection, the temperature of the raceway and the coke bed decreased slightly. Pulverized coal burnout changes little with the hydrogen injection rate increasing from 500 Nm³/h to 1500 Nm³/h, which is because hydrogen combustion promotes pulverized coal at the front part of the raceway but inhibits it at the end due to the relative lack of oxygen. These results will help better understand the combustion behavior in the tuyere and raceway of the blast furnace with oxygen-rich blast and hydrogen injection. Full article

(This article belongs to the Special Issue Advanced Metal Smelting Technology and Prospects)

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11 pages, 7141 KiB

Open AccessArticle

Microstructural Insights into Solid Particle Erosion in a High-Chromium Cast Iron

by Alessio Suman, Annalisa Fortini and Nicola Zanini

Metals 2025, 15(1), 6; https://doi.org/10.3390/met15010006 - 26 Dec 2024

Abstract

Solid particle erosion (SPE) significantly limits the service life of High-Chromium Cast Irons (HCCIs), widely used in power generation and mining industries. This study investigates how microstructural features influence the erosion resistance of a Fe-Cr-C cast iron, focusing on the interplay between particle [...] Read more.

Solid particle erosion (SPE) significantly limits the service life of High-Chromium Cast Irons (HCCIs), widely used in power generation and mining industries. This study investigates how microstructural features influence the erosion resistance of a Fe-Cr-C cast iron, focusing on the interplay between particle kinetic energy and carbide features, i.e., carbide volume fraction (CVF). Erosion tests, conducted per ASTM G76 standards, revealed that substrates with similar CVFs exhibited varying damage levels, even at consistent particle kinetic energies. The findings underscored that impact conditions have a greater influence on erosion resistance than CVF alone, emphasizing the critical role of carbide morphology and distribution in mitigating damage. This work provides valuable insights for optimizing HCCIs to enhance material performance and durability in demanding erosive environments by tailoring carbide distribution to specific operational conditions. Full article

(This article belongs to the Special Issue Design, Processing and Characterization of Metals and Alloys)

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11 pages, 2416 KiB

Open AccessArticle

The Effect of Annealing in a Magnetic Field on the Microstructures and Magnetic Properties of (Nd_0.8RE_0.2)_2.2Fe₁₂Co₂B (RE = La, Ce) Alloys

by Xiaohua Tan, Xuanbo Shi, Shiqi Zhang and Hui Xu

Metals 2025, 15(1), 5; https://doi.org/10.3390/met15010005 - 26 Dec 2024

Abstract

The development of high-performance and cost-effective Nd-Fe-B permanent magnets is crucial to meet the ever-growing requirements of renewable and clean energy applications. Here, we use low-cost and highly abundant La and Ce to partially substitute Nd and investigate the effect of annealing treatment [...] Read more.

The development of high-performance and cost-effective Nd-Fe-B permanent magnets is crucial to meet the ever-growing requirements of renewable and clean energy applications. Here, we use low-cost and highly abundant La and Ce to partially substitute Nd and investigate the effect of annealing treatment with a 1 tesla (T) magnetic field on the microstructures and magnetic properties of (Nd_0.8RE_0.2)_2.2Fe₁₂Co₂B (RE = La, Ce) ribbons. The remanence (B_r) and maximum energy product ((BH)_max) of studied alloys can be improved by magnetic field annealing. The respective B_r and (BH)_max of annealed (Nd_0.8La_0.2)_2.2Fe₁₂Co₂B alloy are increased to 0.86 T and 124 kJ/m³. In comparison to melt-spun (Nd_0.8Ce_0.2)_2.2Fe₁₂Co₂B alloy, the B_r and (BH)_max of the magnetic field-annealed alloy are improved by 5% and 8%. The underlying mechanism of improved magnetic properties of La- and Ce-substituted alloys is different. The interaction magnetic domain size in (Nd_0.8La_0.2)_2.2Fe₁₂Co₂B alloy can be increased by magnetic field annealing, leading to the enhancement of exchange coupling interaction, which results to the improvement in B_r and (BH)_max. In the (Nd_0.8Ce_0.2)_2.2Fe₁₂Co₂B alloy, the concentration of (Fe + Co) of ferromagnetic intergranular phase is increased after magnetic field annealing, resulting in the increase in B_r and (BH)_max. Full article

(This article belongs to the Special Issue Magnetic Properties Analysis of Amorphous and Partially Crystallized Alloys)

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10 pages, 2335 KiB

Open AccessArticle

Microstructure Formation and Dry Reciprocating Sliding Wear Response of High-Entropy Hypereutectic White Cast Irons

by Willian Martins Pasini, Wojciech Polkowski, Tomasz Dudziak, Carlos Alexandre dos Santos and Vinicius Karlinski de Barcellos

Metals 2025, 15(1), 4; https://doi.org/10.3390/met15010004 - 26 Dec 2024

Abstract

White cast irons (WCI) are widely used in industries requiring high wear resistance due to their microstructure consisting of hard carbides dispersed within a metallic matrix. This study focuses on developing wear-resistant multi-component hypereutectic high chromium cast irons, merging concepts of high entropy [...] Read more.

White cast irons (WCI) are widely used in industries requiring high wear resistance due to their microstructure consisting of hard carbides dispersed within a metallic matrix. This study focuses on developing wear-resistant multi-component hypereutectic high chromium cast irons, merging concepts of high entropy alloys with the conventional metallurgy of white cast irons, specifically exploring the influence of carbide-forming elements such as V, Mo, and Ni on solidification behavior, microstructure, and wear performance. The research investigates the solidification process of the alloys using Computer-Aided Cooling Curve Analysis (CA-CCA) and characterizes the microstructures through X-ray diffraction (XRD) and scanning electron microscopy (SEM). The wear behavior of the developed alloys is evaluated through reciprocating sliding wear tests, revealing the impact of varying chemical compositions on wear resistance. The results demonstrate that high-entropy white cast iron (HEWCI), particularly those enriched with carbide-forming elements, exhibit superior abrasion resistance compared to conventional high-chromium cast irons. The alloy with 2 Mo and 4 V content showed the best performance, presenting the lowest wear rate (61.5% lower than HCCI alloy) and CoF (values ranging from 0.20 to 0.22) due to the highest concentration of V carbides. Full article

(This article belongs to the Special Issue Casting Alloy Design and Characterization—2nd Edition)

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26 pages, 5867 KiB

Open AccessArticle

On Transformation and Stress–Strain–Temperature Behavior of Fine-Grained Ni-Rich NiTi Wire vs. Aging Mode

by Elena Ryklina, Kristina Polyakova, Victor Komarov, Semen Murygin, Anton Konopatsky, Vladimir Andreev and Adilet Ulanov

Metals 2025, 15(1), 3; https://doi.org/10.3390/met15010003 - 25 Dec 2024

Abstract

The present study was carried out using a cold-drawn wire of Ni_50.8Ti at.% subjected to post-deformation solution treatment at 700 °C for 1 h to obtain a fine-grained recrystallized structure. Subsequent aging was carried out at a temperature range of 300, [...] Read more.

The present study was carried out using a cold-drawn wire of Ni_50.8Ti at.% subjected to post-deformation solution treatment at 700 °C for 1 h to obtain a fine-grained recrystallized structure. Subsequent aging was carried out at a temperature range of 300, 430, and 500 °C for 1, 10, and 20 h. The time–temperature aging mode strongly affects the aging-induced microstructure. Variation of the aging-induced microstructure (using various aging modes) permits precise tuning of the characteristic temperature of the martensitic transformations and their specific temperature ranges upon cooling and heating. The latent heat and hysteresis exhibit different evolution vs. aging durations; this finding remains fair when using different aging temperatures. The aging mode strongly affects the stress–temperature behavior: (i) a dramatical expansion of the temperature range of realization of the transformation yield stress (σ_tr); and (ii) the magnitude of σ_tr at a chosen test temperature is generally determined by the position of the M_s temperature. An additional contribution of competing factors is discussed. The efficiency of the aging temperature under isochronous aging is significantly higher than the efficiency of the aging time under isothermal aging. Aging at 430 °C for 10–20 h provides the highest resource for the recovery strain. The strain–temperature behavior strongly depends on the relative position of the R_s and M_s temperatures (onset of B2→R and R→B19′ transformations, respectively). The regularities obtained can be used to predict the set of functional and mechanical properties of titanium nickelide. Full article

(This article belongs to the Special Issue Heat Treatment, Microstructures, and Mechanical Properties of Metallic Materials)

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16 pages, 5953 KiB

Open AccessArticle

Microstructural and Electrochemical Analysis of the Physically Simulated Heat-Affected Zone of Super-Duplex Stainless Steel UNS S32750

by Francisco Magalhães dos Santos, Jr., Leonardo Oliveira Passos da Silva, Ygor Tadeu Bispo dos Santos, Bruna Callegari, Tiago Nunes Lima and Rodrigo Santiago Coelho

Metals 2025, 15(1), 2; https://doi.org/10.3390/met15010002 - 24 Dec 2024

Abstract

Super-duplex stainless steels (SDSSs) were introduced in the oil and gas industry due to their high resistance to pitting corrosion, promoted by the high content of alloying elements. The welding process can cause an unbalanced ferrite/austenite microstructure and, consequently, the possibility of deleterious [...] Read more.

Super-duplex stainless steels (SDSSs) were introduced in the oil and gas industry due to their high resistance to pitting corrosion, promoted by the high content of alloying elements. The welding process can cause an unbalanced ferrite/austenite microstructure and, consequently, the possibility of deleterious phases, increasing the risk of failure. The aim of this work is to investigate the behavior of the heat-affected zone (HAZ) of SDSS UNS S32750 steel produced with different thermal inputs simulated in a Gleeble^® welding simulator and correlate these findings with its corrosion properties. The pitting resistance was investigated by electrochemical techniques in sodium chloride solution, and the critical pitting temperature (CPT) was calculated for each evaluated microstructure. The material as received presents 46.19 vol% ferrite and a high corrosion resistance, with a CPT of 71.54 °C. HAZ-simulated cycles resulted in similar ferrite percentages, between 54.09 vol% and 57.25 vol%. A relationship was found between heat input, ferrite content, and CPT: increasing the heat input results in greater ferrite content and lowers the CPT, which may favor the pitting corrosion process. Therefore, it is concluded that the ferrite content directly influences the pitting behavior of the material. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels (2nd Edition))

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16 pages, 6797 KiB

Open AccessArticle

Improving the Metal Inert Gas Welding Efficiency and Microstructural Stability in the Butt and Lap Joints of Aluminum Automotive Components Using Sc- and Zr-Enhanced Filler Wires

by Hansol Ko, Hye-Jin Kim, Dong-Yoon Kim and Jiyoung Yu

Metals 2025, 15(1), 1; https://doi.org/10.3390/met15010001 - 24 Dec 2024

Abstract

The grain growth in the fusion zone (FZ) and heat-affected zone (HAZ) of metal inert gas (MIG) welding processes negatively affect the mechanical properties of aluminum alloy MIG welds used in automotive components. Although the addition of Sc- and Zr-based filler wires can [...] Read more.

The grain growth in the fusion zone (FZ) and heat-affected zone (HAZ) of metal inert gas (MIG) welding processes negatively affect the mechanical properties of aluminum alloy MIG welds used in automotive components. Although the addition of Sc- and Zr-based filler wires can refine weld microstructures and enhance the mechanical properties, conditions resembling actual automotive component joints have not been sufficiently investigated. In this study, 5083-O aluminum alloy base material was welded into butt and lap joints using conventional 5000-series aluminum alloy filler wires (Al-5.0Mg) and wires containing Sc and Zr (Al-4.8Mg-0.7Sc-0.3Zr) under various heat input conditions. The mechanical properties of the welds were evaluated via tensile tests, and the microstructures in the FZ and HAZ were analyzed. In butt joints, Al-4.8Mg-0.7Sc-0.3Zr exhibited a finer and more uniform grain structure with increased tensile strength compared with those welded using Al-5.0Mg. The microstructure became coarser with the increased heat input, and the tensile strength tended to decrease. In lap joints, the tensile-shear strength of Al-4.8Mg-0.7Sc-0.3Zr was higher than that of Al-5.0Mg; it further increased with the increase in the amount of deposited metal. The coarsening of the microstructure with the increased heat input was disadvantageous for the tensile-shear strength, and the increased weld size offset the adverse effects of the coarse microstructure. These results indicate that the heat input and the amount of deposited metal must be optimized to ensure stiffness in various joints of automotive components. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels (2nd Edition))

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16 pages, 24622 KiB

Open AccessArticle

Welding Pores Evolution in the Detector Bottom-Locking Structure Fabricated Using the Hybrid Pulsed Arc–Laser Method

by Yonglong Yu, Jianzhou Xu, Xiaoquan Yu, Liang Guo, Tongyu Zhu and Ding Fan

Metals 2024, 14(12), 1469; https://doi.org/10.3390/met14121469 - 23 Dec 2024

Abstract

The welding of the bottom-locking structure in a detector receptacle plays an essential role in ensuring the safety of nuclear equipment. A pulsed TIG–laser hybrid welding method is proposed to address the problem of welding pores in locking structural parts. The effects of [...] Read more.

The welding of the bottom-locking structure in a detector receptacle plays an essential role in ensuring the safety of nuclear equipment. A pulsed TIG–laser hybrid welding method is proposed to address the problem of welding pores in locking structural parts. The effects of the pulse frequency on the escape of porosity and of porosity on the mechanical properties of the hybrid welding joint were investigated. The results were compared to those of direct current (0 Hz), showing that the pulse frequency affects the stability of the arc. With an increase in pulse frequency, the grain size of the fusion zone gradually decreases, and the flow in the middle area of the molten pool increases. This subjects bubbles in the molten pool to a thrust force, which causes the bubbles to escape to the surface of the molten pool. Compared with 0 Hz, the tensile strength of the joint increased by 67%. This provides a new solution for obtaining reliable welded joints for the bottom-locking structure of detector storage tanks. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Property Improvement of Welded Metal Joints)

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