Metals

17 pages, 8531 KB

Open AccessArticle

Numerical Simulation of Bubble Flow in Continuous Casting Mold with Bubble Swarm Correction of Drag Coefficient

by Qingrui Lai, Zhiguo Luo, Yongjie Zhang, Zongshu Zou and Haifeng Li

Metals 2025, 15(9), 952; https://doi.org/10.3390/met15090952 (registering DOI) - 27 Aug 2025

This study employs a numerical simulation approach to investigate argon bubble flow behavior within a steel continuous casting mold, with a focus on the impact of bubble swarm correction models. Three scenarios are compared: one without any correction and two incorporating drag coefficient [...] Read more.

This study employs a numerical simulation approach to investigate argon bubble flow behavior within a steel continuous casting mold, with a focus on the impact of bubble swarm correction models. Three scenarios are compared: one without any correction and two incorporating drag coefficient corrections, specifically designed for bubble swarm effects. The results demonstrate that incorporating these correction models significantly improves the predictive accuracy of simulations. In particular, the inclusion of a bubble swarm correction model reduces the error in predicted bubble trajectories by 51.7% and 23.0%, respectively, when measured by Hausdorff distances against experimental trajectory data, compared to the scenario without corrections. These findings underline the importance of selecting an appropriate drag correction model for accurate simulations of bubble dynamics and their interaction with the liquid steel in continuous casting molds. This study highlights that drag correction models tailored to the specific conditions of the continuous casting process are essential for achieving realistic predictions. Full article

(This article belongs to the Special Issue Advanced Simulation and Modeling Technologies of Metallurgical Processes—2nd Edition)

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14 pages, 3281 KB

Open AccessArticle

Research on the Johnson–Cook Constitutive Model and Failure Behavior of TC4 Alloy

by Jiaxuan Zhu, Huidong Zhi, Tong Huang, Ning Ding and Zhaoming Yan

Metals 2025, 15(9), 951; https://doi.org/10.3390/met15090951 (registering DOI) - 27 Aug 2025

Abstract

This study investigates the mechanical response characteristics and damage evolution behavior of TC4 alloy through quasi-static/dynamic coupled experimental methods. Quasi-static tensile tests at varying temperatures (293 K, 423 K, and 623 K) were conducted using a universal testing machine, while room-temperature dynamic tensile [...] Read more.

This study investigates the mechanical response characteristics and damage evolution behavior of TC4 alloy through quasi-static/dynamic coupled experimental methods. Quasi-static tensile tests at varying temperatures (293 K, 423 K, and 623 K) were conducted using a universal testing machine, while room-temperature dynamic tensile tests (strain rate 1000–3000 s⁻¹) were performed with a Split Hopkinson Tensile Bar (SHTB). Key findings include the following: (1) Significant temperature-softening effect was observed, with flow stress decreasing markedly as temperature increased; (2) Notch size effect influenced mechanical properties, showing 50% enhancement in post-fracture elongation when notch radius increased from 3 mm to 6 mm; and (3) Strain-hardening effect exhibited rate dependence under dynamic loading, with reduced hardening index within the tested strain rate range. The Johnson–Cook constitutive model and failure criterion were modified and parameterized based on experimental data. A 3D tensile simulation model developed in ABAQUS demonstrated strong agreement with experimental results, achieving a 0.97 correlation coefficient for load–displacement curves, thereby validating the modified models. Scanning electron microscopy (SEM) analysis of fracture surfaces revealed temperature- and strain rate-dependent microstructural characteristics, dominated by ductile fracture mechanisms involving microvoid nucleation, growth, and coalescence. This research provides theoretical foundations for analyzing Ti alloy structures under impact loading through established temperature–rate-coupled constitutive models. Full article

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

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12 pages, 11445 KB

Open AccessArticle

Thermal Characterisation of Hybrid Laser Welds Made of Conventionally and Additively Soft Martensitic Steel 1.4313

by Indira Dey, Thomas Mayer, Bianca Egli, Damian Klingler and Konrad Wegener

Metals 2025, 15(9), 950; https://doi.org/10.3390/met15090950 (registering DOI) - 27 Aug 2025

Abstract

Part segmentation can be used to overcome limitations of additive manufacturing (AM) processes such as Direct Energy Deposition of Metals (DED). In this case subparts of soft martensitic steel 1.4313 produced by conventional manufacturing (CM) and AM are joined by laser welding. This [...] Read more.

Part segmentation can be used to overcome limitations of additive manufacturing (AM) processes such as Direct Energy Deposition of Metals (DED). In this case subparts of soft martensitic steel 1.4313 produced by conventional manufacturing (CM) and AM are joined by laser welding. This paper reports the difference in thermal conductivity of conventional and additive manufactured parts. The thermal conductivity was calculated from the thermal diffusivity, the specific heat, and the bulk density. Furthermore, the temperature was measured during welding and the microstructure analyzed. The far field temperature was measured using eight K-type thermocouples and the microstructure was analyzed by metallography and light microscopy. The results showed that the thermal conductivity of AM material is 8% lower and therefore the heating rate 5% lower compared to CM material. The lower thermal conductivity is explained in the literature by its higher dislocation density, unfavorable alloying element distribution and a lower rest austenite content. AM introduces structural complexity that hampers electron and phonon transport, thereby reducing the thermal conductivity despite similar base chemical compositions. The heat-affected zone is only clearly visible on the CM side due to carbide formation. In DED parts, it comes to different phases in non-equilibrium states, which complicates the identification of carbides and the HAZ. The findings are important for the design of hybrid components to improve the the joint integrity and functionality of hybrid parts. Full article

(This article belongs to the Section Additive Manufacturing)

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17 pages, 18603 KB

Open AccessArticle

High-Temperature Mechanical Properties and the Portevin–Le Chatelier Effect for Wire Arc Additively Manufactured Inconel 718 Superalloy

by Run-Hua Song, Xin Zhang, Ya-Jin Yang, Qing-Wen Zhou, Liang Zhang, Hai-Long Qin, Dong-Feng Li and Rong-Pei Shi

Metals 2025, 15(9), 949; https://doi.org/10.3390/met15090949 (registering DOI) - 27 Aug 2025

Abstract

In this study, high-temperature uniaxial tensile tests were performed on IN718 superalloy samples fabricated using Wire Arc Additive Manufacturing (WAAM) and compared to wrought IN718 superalloy samples. The mechanical properties and Portevin–Le Chatelier (PLC) behavior of WAAM IN718 were analyzed, with particular attention [...] Read more.

In this study, high-temperature uniaxial tensile tests were performed on IN718 superalloy samples fabricated using Wire Arc Additive Manufacturing (WAAM) and compared to wrought IN718 superalloy samples. The mechanical properties and Portevin–Le Chatelier (PLC) behavior of WAAM IN718 were analyzed, with particular attention paid to its anisotropy and differences from its wrought counterpart. WAAM specimens were obtained from three distinct orientations within the printed blocks. The results indicated that WAAM IN718 exhibited a higher yield strength but reduced failure elongation compared to wrought IN718. Among the WAAM samples, the yield strength was highest in the transverse direction, followed by the in-depth direction, and lowest in the growth direction. Post-aging treatment significantly increased the yield strength of WAAM IN718. WAAM IN718 showed a larger critical strain for the onset of serrated flow and smaller stress drop amplitudes compared to wrought IN718 under the PLC effect. Furthermore, as the strain rate decreased, PLC serrations in WAAM specimens from the in-depth direction transitioned from type A to type C. Conversely, specimens from the growth direction maintained type B serrations at a strain rate of

10^{- 4} s^{- 1}

. This study also examined potential factors influencing the differences in PLC behavior and conducted an analysis of the fracture surfaces across various specimens. Full article

(This article belongs to the Special Issue Innovations and Challenges in Wire Arc Additive Manufacturing of High-Performance Metals and Alloys)

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20 pages, 6138 KB

Open AccessArticle

Sequential Redox Precipitation and Solvent Extraction for Comprehensive Metal Recovery from Spent High Manganese Lithium-Ion Battery

by Jiawei Zhang, Fupeng Liu, Chunfa Liao, Tao Zhang, Feixiong Chen, Hao Wang and Yuxin Gao

Metals 2025, 15(9), 948; https://doi.org/10.3390/met15090948 - 26 Aug 2025

Abstract

The traditional recycling process of spent lithium-ion battery(LIB) with high Mn content faces the defects of high cost of neutralization and precipitation, poor economics of Mn extraction, and serious Li loss. Therefore, this paper introduces a comprehensive hydrometallurgical method for extracting valuable metals [...] Read more.

The traditional recycling process of spent lithium-ion battery(LIB) with high Mn content faces the defects of high cost of neutralization and precipitation, poor economics of Mn extraction, and serious Li loss. Therefore, this paper introduces a comprehensive hydrometallurgical method for extracting valuable metals from high-Mn spent LIB. Particularly, directional precipitation of Mn was achieved by utilizing its redox properties, and shot-process extraction and enrichment of Li was realized by using the extractant HBL121. In a sulfuric acid system, control of the oxidant dosage to 0.8% resulted in high leaching efficiencies for Li, Ni, Co, and Mn, with values of 96.58%, 96.13%, 95.22%, and 94.24%, respectively, under optimal conditions which were C(H₂SO₄) of 3.5 mol/L, V(H₂O₂) of 0.8% (v/v), L/S of 10:1, temperature of 60 °C, and time of 60 min. Subsequently, the addition of KMnO₄ dosage (K_p/K_t) in a ratio of 1:1 resulted in the precipitation of 98.47% of Mn as MnO₂, with Ni and Li precipitation efficiencies of 0.2% and 0.1%, respectively. Cascade extraction of Ni and Co was reached by using Cyanex272 extractant from the solution after Mn precipitation. At an organic-to-aqueous phase ratio (O/A) of 1:5, the Co extraction efficiency reached 98.68%, whereas the loss efficiency of Ni was 5.53%, and Li was less than 0.1%. Adjusting the O/A to 1:1 increased the Ni extraction efficiency to 89.99% and Li loss to 8.95%. Finally, the HBL121 extractant was utilized to extract Li from the Li-rich solution, achieving 95.08% extraction efficiency. The Li was stripped with 2 mol/L H₂SO₄ from the load organic phase, realizing a Li concentration of 11.44 g/L. Thus, this process facilitates the comprehensive and efficient recovery of valuable metals such as Li, Ni, Co, and Mn from spent high-Mn LIB. Full article

(This article belongs to the Special Issue Deposition of Metals and Their Application in Catalytic Processes of Energy Interest (2nd Edition))

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15 pages, 3858 KB

Open AccessArticle

Cyclic HCP<->FCC Phase Transformation Crystallography in Pure Cobalt

by Yuhang Huang, Jinjiang He, Zhiyi Zhu, Guojin Xu, Qiqi Qi, Junfeng Luo, Zaiyan Shang and Xinfu Gu

Metals 2025, 15(9), 947; https://doi.org/10.3390/met15090947 - 26 Aug 2025

Abstract

The phase transformations between HCP and FCC structures are among the most important transformations in metallic materials. The memory effect during cyclic transformation around the transus temperature in pure cobalt was investigated using the in situ electron backscatter diffraction (EBSD) technique. The crystallographic [...] Read more.

The phase transformations between HCP and FCC structures are among the most important transformations in metallic materials. The memory effect during cyclic transformation around the transus temperature in pure cobalt was investigated using the in situ electron backscatter diffraction (EBSD) technique. The crystallographic variants of orientation were systematically derived and compared with the observations. Texture memory effect was observed at both room and high temperatures, and a notable variant selection was observed, with the microstructure being preserved after cyclic heat treatment. Based on EBSD observations, the transformation mechanism is explained based on nucleation from a crystallographic perspective. Restricted nucleation of the transformation variants by grain boundaries is proposed to explain the observed phenomena, and these proposals could be extended to similar transformation systems. Full article

(This article belongs to the Special Issue Thermodynamics and Kinetics Analysis of Metallic Material)

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21 pages, 12608 KB

Open AccessArticle

Reverse Engineering of Laser Welding Process Parameters for Ti6Al4V Alloy Based on Machine Learning

by Fei Li, Yuan Liu, Zheng Ren, Xiong Zhang and Yanqiu Zhao

Metals 2025, 15(9), 946; https://doi.org/10.3390/met15090946 - 26 Aug 2025

Abstract

The mechanical performance of laser-welded Ti6Al4V alloy joints is governed by multiple process parameters with complex interplay, leading to nonlinear correlations, that complicate the quest for optimal parameters. In this paper, a reverse engineering model for process parameters was developed using backpropagation (BP) [...] Read more.

The mechanical performance of laser-welded Ti6Al4V alloy joints is governed by multiple process parameters with complex interplay, leading to nonlinear correlations, that complicate the quest for optimal parameters. In this paper, a reverse engineering model for process parameters was developed using backpropagation (BP) neural networks, targeting mechanical properties as the optimization objective for inverse parameter design. The BP neural network was enhanced via differential evolution tuning, achieving significant improvements in both mechanical property prediction and process parameter inversion. The prediction model demonstrated a relative error of approximately 3%, whereas the inverse model exhibited an error of about 6% under varying process conditions. A novel hybrid BP-WC model was then proposed by fusing weight coefficients from both the prediction and inverse models. This model reduced the inverse error of process parameters to 3%, providing a robust framework for efficient parameter optimization in laser welding for Ti6Al4V alloy. Full article

(This article belongs to the Special Issue Advanced Laser Welding and Joining of Metallic Materials)

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18 pages, 2988 KB

Open AccessArticle

Fatigue Prediction Method of Superalloy Based on the Improved Largest Lyapunov Exponent

by Ting Jing and Yang Yu

Metals 2025, 15(9), 945; https://doi.org/10.3390/met15090945 - 26 Aug 2025

Abstract

The crack growth process in metals can be continuously monitored and recorded in real time using highly sensitive acoustic emission technology. To predict this complex behavior, an improved largest Lyapunov exponent method, enhanced by a small data optimization approach named the small data [...] Read more.

The crack growth process in metals can be continuously monitored and recorded in real time using highly sensitive acoustic emission technology. To predict this complex behavior, an improved largest Lyapunov exponent method, enhanced by a small data optimization approach named the small data method, is applied. Meanwhile, experimental results reveal that the acoustic emission signals collected during the fatigue crack growth process display distinct chaotic characteristics. By employing the small data method and cross-comparison analysis with the traditional Wolf method, the prediction accuracy and efficiency are significantly enhanced, even when only a limited amount of data is available. Compared to conventional techniques, this method demonstrates higher reliability and robustness, offering a powerful tool for early-stage monitoring and life prediction of metallic materials. Full article

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15 pages, 5062 KB

Open AccessArticle

Effect of Induction Hardening Following Carburizing–Nitriding Duplex Treatment on the Microstructure and Fatigue Strength of JIS-SCM420 Low-Alloy Steel

by Minheon Kim and Osamu Umezawa

Metals 2025, 15(9), 944; https://doi.org/10.3390/met15090944 - 25 Aug 2025

Abstract

In this study, a duplex treatment combining carburizing, nitriding, and subsequent induction hardening (IH) was applied to JIS-SCM420 low-alloy steel. A comprehensive evaluation was conducted to assess surface characteristics, including microstructure, hardness, residual stress, and fatigue performance. The IH process successfully produced a [...] Read more.

In this study, a duplex treatment combining carburizing, nitriding, and subsequent induction hardening (IH) was applied to JIS-SCM420 low-alloy steel. A comprehensive evaluation was conducted to assess surface characteristics, including microstructure, hardness, residual stress, and fatigue performance. The IH process successfully produced a high-nitrogen-content ε-Fe_2-3(N,C) compound layer (2–3 μm thick) and fine acicular martensite at the surface, significantly enhancing surface hardness (950 HV0.03) and inducing beneficial compressive residual stress (−477 MPa). The IH-treated material exhibited a plane-bending fatigue strength of approximately 775 MPa, notably higher than that of conventionally carbonitrided specimens (700 MPa). This improvement was primarily attributed to the formation of the hard ε-Fe_2-3(N,C) compound layer and refined martensitic structure resulting from induction hardening. Additionally, IH activated residual interstitial elements, promoting the precipitation of stable surface nitrides. These microstructural changes effectively suppressed fatigue crack initiation and propagation, thereby extending fatigue life under cyclic loading conditions. Full article

(This article belongs to the Special Issue Advances in the Fatigue and Fracture Behaviour of Metallic Materials)

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13 pages, 3915 KB

Open AccessArticle

Simultaneous Improvement of Glass-Forming Ability and Ductility in Co-Based BMGs Through Si/Fe Microalloying

by Xinlong Quan, Liming Xu, Yong Zhao, Xuecheng Tang, Qing Liu, Bo Zhang and Wei-Hua Wang

Metals 2025, 15(9), 943; https://doi.org/10.3390/met15090943 - 25 Aug 2025

Abstract

Cobalt-based bulk metallic glasses (Co-based BMGs) offer a combination of high strength, corrosion resistance, and soft magnetic properties, yet their limited glass-forming ability (GFA) and poor room-temperature ductility restrict broader application. In this study, a microalloying strategy was applied to the Co₆₁ [...] Read more.

Cobalt-based bulk metallic glasses (Co-based BMGs) offer a combination of high strength, corrosion resistance, and soft magnetic properties, yet their limited glass-forming ability (GFA) and poor room-temperature ductility restrict broader application. In this study, a microalloying strategy was applied to the Co₆₁Nb₈B₃₁ base composition to develop Co-Nb-B-Si and Co-Fe-Nb-B-Si systems. The effects of Si addition and Fe substitution on GFA, thermal stability, and mechanical properties were systematically investigated. Si doping combined with Co/B ratio tuning broadened the supercooled liquid region and increased the critical glass-forming diameter from 1 mm to 3 mm. Further addition of 5 at.% Fe expanded the supercooled liquid region and enabled the fabrication of a fully amorphous plate with 1 mm thickness. The optimized Co₆₃Nb₈B₂₇Si₂ alloy exhibited a compressive strength of 5.18 GPa and a plastic strain of 3.81%. Fracture surface analysis revealed ductile fracture features in the Si-containing alloy and brittle characteristics in Fe-rich compositions. These results demonstrate that microalloying is effective in optimizing the balance between GFA and mechanical performance of Co-based BMGs, offering guidance for composition and processing design. Full article

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20 pages, 5426 KB

Open AccessArticle

Optimization of Rare Earth Yield from Fluoride Roasting of Neodymium–Iron–Boron Waste Using Response Surface Methodology

by Youwei Liu, Dewei Li, Xiang Lei, Jinliang Wang and Yanfei Xiao

Metals 2025, 15(9), 942; https://doi.org/10.3390/met15090942 - 25 Aug 2025

Abstract

To address the critical challenges in pyrometallurgical recycling processes—such as poor feedstock adaptability, high energy consumption during roasting conversion, and the low added value of rare earth products—this study systematically investigated the mechanism and process optimization of ammonium bifluoride (NH₄HF₂ [...] Read more.

To address the critical challenges in pyrometallurgical recycling processes—such as poor feedstock adaptability, high energy consumption during roasting conversion, and the low added value of rare earth products—this study systematically investigated the mechanism and process optimization of ammonium bifluoride (NH₄HF₂) roasting for the recovery of neodymium–iron–boron (NdFeB) waste. Thermodynamic analysis confirmed the feasibility of the conversion reaction between NH₄HF₂ and the rare earth components in NdFeB waste. Single-factor experiments were conducted to examine the effects of roasting temperature, reaction time, and NH₄HF₂ dosage on rare earth recovery. The optimal conditions were a roasting temperature of 600 °C, a reaction time of 120 min, and a NH₄HF₂ dosage of 75 wt%, achieving a rare earth recovery rate of 98.81%. Furthermore, the response surface methodology (RSM) was employed to establish a quantitative model correlating process parameters with recovery efficiency. Variance analysis demonstrated that the model was highly significant (F = 136.94, p < 0.0001), with excellent agreement between actual and predicted values (R² = 0.9944). Factor contribution analysis revealed that NH₄HF₂ dosage had the most pronounced impact on rare earth fluorination, followed by roasting temperature and reaction time. Under optimized conditions, the purified rare earth fluoride obtained after acid leaching reached a purity of 99.43%, providing high-quality raw material for producing high-value-added rare earth products. Full article

(This article belongs to the Section Extractive Metallurgy)

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21 pages, 11638 KB

Open AccessArticle

The Influence of Manufacturing Parameters and Heat Treatments on the Properties of AlSi10Mg Alloy Produced Using L-PBF

by Gleicy de Lima Xavier Ribeiro, Luis Reis, Rene de Oliveira, Marcos Massi, Rodolfo Luiz Gonçalves and Antônio Augusto Couto

Metals 2025, 15(9), 941; https://doi.org/10.3390/met15090941 - 25 Aug 2025

Abstract

AlSi10Mg has been one of the most studied and employed aluminum alloys for additive manufacturing via laser powder-bed fusion (L-PBF). The optimization of manufacturing parameters is important for reducing internal defects, including porosity and inadequate surface finishes. In addition, heat treatments, such as [...] Read more.

AlSi10Mg has been one of the most studied and employed aluminum alloys for additive manufacturing via laser powder-bed fusion (L-PBF). The optimization of manufacturing parameters is important for reducing internal defects, including porosity and inadequate surface finishes. In addition, heat treatments, such as T6, are often applied to this alloy, but they degrade the characteristic microstructure obtained via L-PBF additive manufacturing—the fine cellular structures—which may, in turn, detrimentally affect the material’s properties. In this context, a new alternative to this treatment, direct aging (DA), has shown promise in improving the mechanical properties of AlSi10Mg parts produced via L-PBF, since it preserves the cellular microstructure, precipitating silicon-rich nanoparticles within the cells. Understanding how different temperatures and heat treatment times influence the microstructure and, consequently, the properties remains a field to be explored in order to optimize the treatment conditions and achieve better mechanical properties. Thus, the objective of this study was to evaluate the influence of manufacturing parameters and heat treatments on the microstructure and mechanical properties of AlSi10Mg alloy. The optimized manufacturing conditions were 300 W power, 800 mm/s scan speed, 30 µm layer thickness, and an argon atmosphere, which led to lower porosity and better finishing. Samples were heat-treated via DA at 150 °C and 170 °C for different times, as well as undergoing a T6 treatment (solution at 520 °C followed by aging at 150 °C and 170 °C). Initially, the aging curves show higher hardness values for the direct aging condition, compared to the T6 and as-built conditions, reaching a peak hardness of 195 HV for 6h of direct aging. In this way, it was followed with microstructural characterization, which demonstrated that DA maintained the fine cell microstructure of L-PBF and promoted the precipitation of Si nanoparticles, which certainly contributed to the increase in hardness compared to T6, which promoted a structure with coarser precipitates. DA at 170 °C for 6 h increased the tensile strength to 430 MPa, compared to the as-built condition, with a slight loss of ductility. Full article

(This article belongs to the Special Issue Light Alloy and Its Application (2nd Edition))

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18 pages, 8946 KB

Open AccessArticle

by Mazin Oheil, Dulal Saha, Hamid Jahed and Adrian Gerlich

Metals 2025, 15(9), 940; https://doi.org/10.3390/met15090940 - 24 Aug 2025

Abstract

Direct fusion welding of aluminum (Al) to magnesium (Mg) results in the formation of brittle intermetallic compounds (IMCs) that significantly restrict the application of these joints in structural applications. In this study, cold spray, a promising solid-state coating deposition technology, was employed to [...] Read more.

Direct fusion welding of aluminum (Al) to magnesium (Mg) results in the formation of brittle intermetallic compounds (IMCs) that significantly restrict the application of these joints in structural applications. In this study, cold spray, a promising solid-state coating deposition technology, was employed to introduce a nickel (Ni) interlayer to facilitate joining of Al to Mg sheets by means of resistance spot welding (RSW). The ability of cold spraying to deposit metallic powder on the substrate without melting proves beneficial in mitigating the formation of the Al-Mg IMCs. The Ni-coated coupons were subsequently welded via resistance spot welding at optimized parameters: 27 kA for 15 cycles in two pulses with a 5-cycle inter-pulse delay. Scanning electron microscopy confirmed metallurgical bonding between the Al, Mg, and Ni coatings in the fusion zone. It is shown that the bonding between the three elements inhibits the formation of deleterious IMCs. Tensile shear testing showed joint strength exceeding 4.2 kN, highlighting the potential of the proposed cold spray RSW approach for dissimilar joining in structural applications. Full article

(This article belongs to the Special Issue Novel Insights into Welding and Joining Technologies of Metallic Materials)

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12 pages, 4386 KB

Open AccessArticle

The Role of Local Orientations Gradients in the Formation of the Recrystallisation Texture in Cold-Rolled IF Steel

by Estefania A. Sepulveda Hernández, Felipe M. Castro Cerda and Leo A. I. Kestens

Metals 2025, 15(9), 939; https://doi.org/10.3390/met15090939 - 24 Aug 2025

Abstract

This study investigates the subsequent stages of recrystallisation in Interstitial-Free (IF) steel subjected to an unconventional continuous annealing process with a controlled thermal gradient. A cold-rolled steel strip was exposed to varying annealing temperatures along its length, enabling the analysis of microstructural evolution [...] Read more.

This study investigates the subsequent stages of recrystallisation in Interstitial-Free (IF) steel subjected to an unconventional continuous annealing process with a controlled thermal gradient. A cold-rolled steel strip was exposed to varying annealing temperatures along its length, enabling the analysis of microstructural evolution during the course of recrystallisation. The microstructure and stored energy were assessed at various positions along the strip using Electron Backscatter Diffraction (EBSD). The results underscore the significant influence of local misorientation and structural inhomogeneity on orientation selection during recrystallisation. The remaining non-recrystallised volume fraction (NRF) strongly correlates with the average misorientation gradient, obeying a phenomenological power-law correspondence with an exponent of ~3.7. This indicates that the recrystallisation process is highly sensitive to small changes in local orientation gradients. These findings highlight the crucial role of stored energy distribution for texture evolution, particularly during the early stages of recrystallisation in continuous annealing. It is observed that g-fiber grains, in comparison to a-fiber grains, are much more susceptible to grain fragmentation and therefore develop more robust intra-granular misorientation gradients, allowing for successful nucleation events to occur. In the present study, these phenomena are documented in a statistically representative manner. These insights are valuable for optimising thermal processing in interstitial-free (IF) steels. Full article

(This article belongs to the Special Issue Microstructure, Crystallography, and Mechanical Properties of Metallic Materials)

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21 pages, 4331 KB

Open AccessArticle

An Experimental and Simulation Study on the Effect of Adhesive in Weld Bonded Spot Weld Joints

by Aravinthan Arumugam, Cosmas Pandit Pagwiwoko, Alokesh Pramanik and Animesh Kumar Basak

Metals 2025, 15(9), 938; https://doi.org/10.3390/met15090938 - 24 Aug 2025

Abstract

The use of weld bond (WB) joints in automotive manufacturing is gaining popularity for joining similar and dissimilar materials. This study investigated the effect of Sikaflex-252 (Sika Australia Pty Ltd, Perth, Australia) adhesive in DP600 similar steel joints and DP600 and AISI 316 [...] Read more.

The use of weld bond (WB) joints in automotive manufacturing is gaining popularity for joining similar and dissimilar materials. This study investigated the effect of Sikaflex-252 (Sika Australia Pty Ltd, Perth, Australia) adhesive in DP600 similar steel joints and DP600 and AISI 316 stainless steel dissimilar steel joints. An increase in welding current from 7 kA to 10 kA increased the weld diameter and tensile shear strength in the RSW joints and the WB joints. WB joints had bigger weld diameters of 5.39 mm and 4.84 mm, higher tensile shear strengths of 12.3 kN and 6.85 kN, and higher energy absorption before failure of 32.6 J and 24.6 J at 10 kA compared to joints at 7 kA for similar and dissimilar joints, respectively. The use of adhesive increased heat generation at 10 kA welding current, due to the increase in dynamic resistance. At 7 kA welding current, the adhesive could not produce sufficient heat for spot weld development. The use of adhesive narrowed the weldability lobe in dissimilar RSW and WB joints and showed changes in failure mode. In similar RSW joints and WB joints, weldability lobe changes were not observed, and RSW and WB joints had the same fracture mode for the same welding current. WB welds have reduced stress distribution across the weld nugget compared to RSW welds because of the bigger weld diameter of 5.39 mm and lesser sheet bending of 1.13 mm. WB joint failure comprises the adhesive failure at the start and later the spot weld failure, while RSW joint failure is purely due to spot weld failure. Full article

(This article belongs to the Special Issue Advanced Metal Welding and Joining Technologies—2nd Edition)

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12 pages, 4110 KB

Open AccessArticle

Effect of Solution Treatment on Mechanical Properties and Wear Resistance of Alloyed High-Manganese Steel

by Xiya Qiao, Boyong Li, Xiao Han, Xiangyun Zhang and Xin Yang

Metals 2025, 15(9), 937; https://doi.org/10.3390/met15090937 - 24 Aug 2025

Abstract

We explored the effects of different solution treatment temperatures on the microstructure, mechanical properties and wear resistance of alloyed high-manganese steel, as well as the correlations among the three parameters. The results indicated that the average grain size of high-manganese steel first decreases [...] Read more.

We explored the effects of different solution treatment temperatures on the microstructure, mechanical properties and wear resistance of alloyed high-manganese steel, as well as the correlations among the three parameters. The results indicated that the average grain size of high-manganese steel first decreases and then gradually increases with an increasing solution temperature. After solution treatment, the surface hardness of the high-manganese steel is lower than that of untreated steel. At a solution treatment temperature of 1050 °C, the surface hardness value is lowest, at 253.1 HV. In addition, the optimal combination of tensile strength, yield strength and work hardening rate is observed at a solution treatment temperature of 950 °C. The friction performance test results revealed that the average friction coefficient on the surface of the high-manganese steel first decreased and then increased with the increase in solution treatment temperature. After solution treatment at 950 °C, it reached a minimum value 0.273 due to oxidation friction. Meanwhile, the hardness of the steel after friction increased rapidly because of its excellent work hardening ability, so the wear rate was relatively low, approximately 0.223 × 10⁻¹³ m²/N, demonstrating optimal wear resistance. After solution treatment, the average grain size of high-manganese steel changed, and there was a transformation of the wear mechanism; the friction and wear mechanism shifted from a combination of particle wear and fatigue wear to adhesive wear, with particle wear as the auxiliary. Full article

(This article belongs to the Special Issue Novel Insights and Advances in Steels and Cast Irons)

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15 pages, 5772 KB

Open AccessArticle

Study on the Optimization of the Morphology and Nucleation Mechanism of Electroplated Sn-Pb Coatings by the Synergistic Effect of Composite Additives

by Xiangqing Liu, Chenyu Li, Jie Yu, Ruiqi Liu, Min Shang, Xiaolin Su, Jinye Yao and Haitao Ma

Metals 2025, 15(9), 936; https://doi.org/10.3390/met15090936 - 24 Aug 2025

Abstract

This study investigates the synergistic effects of single- and binary-additive systems on the morphology and nucleation mechanism of Sn-Pb alloy electrodeposited coatings. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry were applied in order [...] Read more.

This study investigates the synergistic effects of single- and binary-additive systems on the morphology and nucleation mechanism of Sn-Pb alloy electrodeposited coatings. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry were applied in order to obtain more information on the action mechanisms of single-additive systems (cinnamaldehyde, PEG-2000, gelatin, vanillin) and binary ones (0.1 g/L cinnamaldehyde + 0.2 g/L PEG-2000) in Sn-Pb electroplating. Results showed that the use of binary-additive systems based on cinnamaldehyde and PEG-2000 significantly improved coating quality, leading to a smooth and uniform surface, dense grains, and a near-eutectic composition (Sn 63.10 wt.%, Pb 36.90 wt.%). This was because the composite additive, through synergistic effects, exhibited the highest cathodic polarization and the largest charge transfer resistance (189.20 Ω cm²), thus inhibiting the electrodeposition process of Sn²⁺ and Pb²⁺. Chronoamperometry revealed that, unlike single additives (PEG-2000 or cinnamaldehyde), the binary-additive system promoted a transition of nucleation mode to instantaneous nucleation, accompanied by a decrease in the peak current and an extension of the corresponding time. This study provides a theoretical basis and experimental support for understanding the nucleation mode of Sn-Pb electroplating, as well as optimizing the synergistic mechanism of additives. Full article

(This article belongs to the Special Issue Mechanical Properties and Corrosion Behavior of Metals after Surface Modification)

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20 pages, 6803 KB

Open AccessArticle

Improved Corrosion Resistance of Yttrium-Bearing H13 Steel for Shield Machine Cutter Ring

by Yunxin Wang, Xingwang Feng, Li Zhang and Bin Yang

Metals 2025, 15(9), 935; https://doi.org/10.3390/met15090935 - 23 Aug 2025

Abstract

H13 steel, which was used as the material for shield machine cutter rings, required tempering to attain superior mechanical properties. The Cr-rich carbide that precipitated during the tempering process definitely decreased the corrosion resistance of the steel. Here, we added rare earth Yttrium [...] Read more.

H13 steel, which was used as the material for shield machine cutter rings, required tempering to attain superior mechanical properties. The Cr-rich carbide that precipitated during the tempering process definitely decreased the corrosion resistance of the steel. Here, we added rare earth Yttrium to enhance the corrosion resistance of H13 steel. It was found that the inclusions were modified by adding yttrium in the steel, and the formation of Cr₂₃C₆ at the grain boundaries during tempering was suppressed. Furthermore, SKPFM measurements demonstrated that the surface potential of yttrium-containing inclusion was comparable to that of the surrounding matrix, thereby reducing the pitting susceptibility of H13 steel. Further investigation showed that yttrium decreased the normal stress range at grain boundaries during the tempering process, and effectively prevented C segregation. Thus, the number of Cr-depleted zones was decreased, and grain boundaries with active Cr atoms were increased. These active Cr atoms effectively sealed the ion channels between the matrix and NaCl solution within the Cr-rich oxide layer, thus improving localized corrosion resistance in the NaCl solution. On the other hand, the electrochemical test and SKPFM exhibited that yttrium reduced the potential loss during tempering, minimized the potential degradation of the matrix, and improved the corrosion resistance of H13 steel with yttrium. Accordingly, the corrosion loss of Y-bearing H13 steel was reduced by 46.6%. Full article

(This article belongs to the Special Issue Recent Advances in High-Performance Steel)

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13 pages, 14139 KB

Open AccessArticle

Low-Temperature Tempering to Tailor Microstructure, Mechanical and Contact Fatigue Performance in the Carburized Layer of an Alloy Steel for Heavy-Duty Gears

by Qingliang Li, Jian Wang, Gang Cheng and Qing Tao

Metals 2025, 15(9), 934; https://doi.org/10.3390/met15090934 - 22 Aug 2025

Abstract

Taking a typical carburized alloy steel for heavy-duty gears as the research object, this work regulates carburizing–quenching and tempering processes to conduct a layer-by-layer analysis of gradient-distributed microstructures and mechanical properties in the carburized layer. The effects of tempering temperature on martensite evolution, [...] Read more.

Taking a typical carburized alloy steel for heavy-duty gears as the research object, this work regulates carburizing–quenching and tempering processes to conduct a layer-by-layer analysis of gradient-distributed microstructures and mechanical properties in the carburized layer. The effects of tempering temperature on martensite evolution, mechanical properties, and wear resistance were specifically investigated. Results demonstrate that carburizing–quenching followed by cryogenic treatment generates high-carbon martensite at the surface, progressively transitioning to lath martensite towards the core. Low-temperature tempering promotes fine carbide precipitation, while elevated temperatures cause carbide coarsening. Specimens tempered at 175 °C achieve surface hardness of 800 HV and near-surface compressive yield strength of 2940 MPa. These samples exhibit 13% lower wear mass loss compared to 240 °C tempered counterparts, demonstrating superior wear resistance characterized by relatively flat wear surfaces, uniform contact stress distribution, and reduced cross-sectional plastic deformation zones. Key strengthening mechanisms at lower tempering temperatures involve solution strengthening, dislocation strengthening, and partial precipitation strengthening from carbides. Coherent carbides formed under these conditions impede fatigue dislocation motion via shearing mechanisms to suppress plastic deformation and fatigue crack initiation under contact fatigue stress, thereby enhancing wear performance. Full article

(This article belongs to the Special Issue Recent Advances in Fatigue and Corrosion Properties of Steels)

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