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Keywords = high-energy grain boundaries

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10 pages, 2384 KiB  
Article
Effects of Grain Size on Mechanical Properties of Nanopolycrystalline Fe-Al Alloy
by Xiaoming Liu, Kun Gao, Long Huang, Peng Chen and Jing Yang
Processes 2025, 13(8), 2462; https://doi.org/10.3390/pr13082462 - 4 Aug 2025
Viewed by 11
Abstract
FeAl intermetallic compounds exhibit high application potential in high-voltage transmission lines to withstand external forces such as powerlines’ own gravity and wind force. The ordered crystal structure in FeAl intermetallic compounds endows materials with high strength, but the remarkable brittleness at room temperature [...] Read more.
FeAl intermetallic compounds exhibit high application potential in high-voltage transmission lines to withstand external forces such as powerlines’ own gravity and wind force. The ordered crystal structure in FeAl intermetallic compounds endows materials with high strength, but the remarkable brittleness at room temperature restricts engineering applications. This contradiction is essentially closely related to the deformation mechanism at the nanoscale. Here, we performed molecular dynamics simulations to reveal anomalous grain size effects and deformation mechanisms in nanocrystalline FeAl intermetallic material. Models with grain sizes ranging from 6.2 to 17.4 nm were systematically investigated under uniaxial tensile stress. The study uncovers a distinctive inverse Hall-Petch relationship governing flow stress within the nanoscale regime. This behavior stems from high-density grain boundaries promoting dislocation annihilation over pile-up. Crucially, the material exhibits anomalous ductility at ultra-high strain rates due to stress-induced phase transformation dominating the plastic deformation. The nascent FCC phase accommodates strain through enhanced slip systems and inherent low stacking fault energy with the increasing phase fraction paralleling the stress plateau. Nanoconfinement suppresses the propagation of macroscopic defects while simultaneously suppressing room-temperature brittle fracture and inhibiting the rapid phase transformation pathways at extreme strain rates. These findings provide new theoretical foundations for designing high-strength and high-toughness intermetallic nanocompounds. Full article
(This article belongs to the Section Materials Processes)
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18 pages, 7997 KiB  
Article
Cryogenic Tensile Strength of 1.6 GPa in a Precipitation-Hardened (NiCoCr)99.25C0.75 Medium-Entropy Alloy Fabricated via Laser Powder Bed Fusion
by So-Yeon Park, Young-Kyun Kim, Hyoung Seop Kim and Kee-Ahn Lee
Materials 2025, 18(15), 3656; https://doi.org/10.3390/ma18153656 - 4 Aug 2025
Viewed by 66
Abstract
A (NiCoCr)99.25C0.75 medium entropy alloy (MEA) was developed via laser powder bed fusion (LPBF) using pre-alloyed powder feedstock containing 0.75 at%C, followed by a precipitation heat treatment. The as-built alloy exhibited high density (>99.9%), columnar grains, fine substructures, and strong [...] Read more.
A (NiCoCr)99.25C0.75 medium entropy alloy (MEA) was developed via laser powder bed fusion (LPBF) using pre-alloyed powder feedstock containing 0.75 at%C, followed by a precipitation heat treatment. The as-built alloy exhibited high density (>99.9%), columnar grains, fine substructures, and strong <111> texture. Heat treatment at 700 °C for 1 h promoted the precipitation of Cr-rich carbides (Cr23C6) along grain and substructure boundaries, which stabilized the microstructure through Zener pinning and the consumption of carbon from the matrix. The heat-treated alloy achieved excellent cryogenic tensile properties at 77 K, with a yield strength of 1230 MPa and an ultimate tensile strength of 1.6 GPa. Compared to previously reported LPBF-built NiCoCr-based MEAs, this alloy exhibited superior strength at both room and cryogenic temperatures, indicating its potential for structural applications in extreme environments. Deformation mechanisms at cryogenic temperature revealed abundant deformation twinning, stacking faults, and strong dislocation–precipitate interactions. These features contributed to dislocation locking, resulting in a work hardening rate higher than that observed at room temperature. This study demonstrates that carbon addition and heat treatment can effectively tune the stacking fault energy and stabilize substructures, leading to enhanced cryogenic mechanical performance of LPBF-built NiCoCr MEAs. Full article
(This article belongs to the Special Issue High-Entropy Alloys: Synthesis, Characterization, and Applications)
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12 pages, 2532 KiB  
Article
Efficient Oxygen Evolution Reaction Performance Achieved by Tri-Doping Modification in Prussian Blue Analogs
by Yanhong Ding, Bin Liu, Haiyan Xiang, Fangqi Ren, Tianzi Xu, Jiayi Liu, Haifeng Xu, Hanzhou Ding, Yirong Zhu and Fusheng Liu
Inorganics 2025, 13(8), 258; https://doi.org/10.3390/inorganics13080258 - 2 Aug 2025
Viewed by 162
Abstract
The high cost of hydrogen production is the primary factor limiting the development of the hydrogen energy industry chain. Additionally, due to the inefficiency of hydrogen production by water electrolysis technology, the development of high-performance catalysts is an effective means of producing low-cost [...] Read more.
The high cost of hydrogen production is the primary factor limiting the development of the hydrogen energy industry chain. Additionally, due to the inefficiency of hydrogen production by water electrolysis technology, the development of high-performance catalysts is an effective means of producing low-cost hydrogen. In water electrolysis technology, the electrocatalytic activity of the electrode affects the kinetics of the oxygen evolution reaction (OER) and the hydrogen evolution rate. This study utilizes the liquid phase co-precipitation method to synthesize three types of Prussian blue analog (PBA) electrocatalytic materials: Fe/PBA(Fe4[Fe(CN)6]3), Fe-Mn/PBA((Fe, Mn)3[Fe(CN)6]2·nH2O), and Fe-Mn-Co/PBA((Mn, Co, Fe)3II[FeIII(CN)6]2·nH2O). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that Fe-Mn-Co/PBA has a smaller particle size and higher crystallinity, and its grain boundary defects provide more active sites for electrochemical reactions. The electrochemical test shows that Fe-Mn-Co/PBA exhibits the best electrochemical performance. The overpotential of the oxygen evolution reaction (OER) under 1 M alkaline electrolyte at 10/50 mA·cm−2 is 270/350 mV, with a Tafel slope of 48 mV·dec−1, and stable electrocatalytic activity is maintained at 5 mA·cm−2. All of these are attributed to the synergistic effect of Fe, Mn, and Co metal ions, grain refinement, and the generation of grain boundary defects and internal stresses. Full article
(This article belongs to the Special Issue Novel Catalysts for Photoelectrochemical Energy Conversion)
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18 pages, 5843 KiB  
Article
Microstructure Evolution in Homogenization Heat Treatment of Inconel 718 Manufactured by Laser Powder Bed Fusion
by Fang Zhang, Yifu Shen and Haiou Yang
Metals 2025, 15(8), 859; https://doi.org/10.3390/met15080859 (registering DOI) - 31 Jul 2025
Viewed by 121
Abstract
This study systematically investigates the homogenization-induced Laves phase dissolution kinetics and recrystallization mechanisms in laser powder bed fusion (L-PBF) processed IN718 superalloy. The as-built material exhibits a characteristic fine dendritic microstructure with interdendritic Laves phase segregation and high dislocation density, featuring directional sub-grain [...] Read more.
This study systematically investigates the homogenization-induced Laves phase dissolution kinetics and recrystallization mechanisms in laser powder bed fusion (L-PBF) processed IN718 superalloy. The as-built material exhibits a characteristic fine dendritic microstructure with interdendritic Laves phase segregation and high dislocation density, featuring directional sub-grain boundaries aligned with the build direction. Laves phase dissolution demonstrates dual-stage kinetics: initial rapid dissolution (0–15 min) governed by bulk atomic diffusion, followed by interface reaction-controlled deceleration (15–60 min) after 1 h at 1150 °C. Complete dissolution of the Laves phase is achieved after 3.7 h at 1150 °C. Recrystallization initiates preferentially at serrated grain boundaries through boundary bulging mechanisms, driven by localized orientation gradients and stored energy differentials. Grain growth kinetics obey a fourth-power time dependence, confirming Ostwald ripening-controlled boundary migration via grain boundary diffusion. Such a study is expected to be helpful in understanding the microstructural development of L-PBF-built IN718 under heat treatments. Full article
(This article belongs to the Section Additive Manufacturing)
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15 pages, 5275 KiB  
Article
Effect of Copper in Gas-Shielded Solid Wire on Microstructural Evolution and Cryogenic Toughness of X80 Pipeline Steel Welds
by Leng Peng, Rui Hong, Qi-Lin Ma, Neng-Sheng Liu, Shu-Biao Yin and Shu-Jun Jia
Materials 2025, 18(15), 3519; https://doi.org/10.3390/ma18153519 - 27 Jul 2025
Viewed by 310
Abstract
This study systematically evaluates the influence of copper (Cu) addition in gas-shielded solid wires on the microstructure and cryogenic toughness of X80 pipeline steel welds. Welds were fabricated using solid wires with varying Cu contents (0.13–0.34 wt.%) under identical gas metal arc welding [...] Read more.
This study systematically evaluates the influence of copper (Cu) addition in gas-shielded solid wires on the microstructure and cryogenic toughness of X80 pipeline steel welds. Welds were fabricated using solid wires with varying Cu contents (0.13–0.34 wt.%) under identical gas metal arc welding (GMAW) parameters. The mechanical capacities were assessed via tensile testing, Charpy V-notch impact tests at −20 °C and Vickers hardness measurements. Microstructural evolution was characterized through optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Key findings reveal that increasing the Cu content from 0.13 wt.% to 0.34 wt.% reduces the volume percentage of acicular ferrite (AF) in the weld metal by approximately 20%, accompanied by a significant decline in cryogenic toughness, with the average impact energy decreasing from 221.08 J to 151.59 J. Mechanistic analysis demonstrates that the trace increase in the Cu element. The phase transition temperature and inclusions is not significant but can refine the prior austenite grain size of the weld, so that the total surface area of the grain boundary increases, and the surface area of the inclusions within the grain is relatively small, resulting in the nucleation of acicular ferrite within the grain being weak. This microstructural transition lowers the critical crack size and diminishes the density for high-angle grain boundaries (HAGBs > 45°), which weakens crack deflection capability. Consequently, the crack propagation angle decreases from 54.73° to 45°, substantially reducing the energy required for stable crack growth and deteriorating low-temperature toughness. Full article
(This article belongs to the Section Metals and Alloys)
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28 pages, 17257 KiB  
Article
A Crystal Plasticity Phase-Field Study on the Effects of Grain Boundary Degradation on the Fatigue Behavior of a Nickel-Based Superalloy
by Pengfei Liu, Zhanghua Chen, Xiao Zhao, Jianxin Dong and He Jiang
Materials 2025, 18(14), 3309; https://doi.org/10.3390/ma18143309 - 14 Jul 2025
Viewed by 374
Abstract
Grain boundary weakening in high-temperature environments significantly influences the fatigue crack growth mechanisms of nickel-based superalloys, introducing challenges in accurately predicting fatigue life. In this study, a dislocation-density-based crystal plasticity phase-field (CP–PF) model is developed to simulate the fatigue crack growth behavior of [...] Read more.
Grain boundary weakening in high-temperature environments significantly influences the fatigue crack growth mechanisms of nickel-based superalloys, introducing challenges in accurately predicting fatigue life. In this study, a dislocation-density-based crystal plasticity phase-field (CP–PF) model is developed to simulate the fatigue crack growth behavior of the GH4169 alloy under both room and elevated temperatures. Grain boundaries are explicitly modeled, enabling the competition between transgranular and intergranular cracking to be accurately captured. The grain boundary separation energy and surface energy, calculated via molecular dynamics simulations, are employed as failure criteria for grain boundary and intragranular material points, respectively. The simulation results reveal that under oxygen-free conditions, fatigue crack propagation at both room and high temperatures is governed by sustained shear slip, with crack advancement hindered by grains exhibiting low Schmid factors. When grain boundary oxidation is introduced, increasing oxidation levels progressively degrade grain boundary strength and reduce overall fatigue resistance. Specifically, at room temperature, oxidation shortens the duration of crack arrest near grain boundaries. At elevated service temperatures, intensified grain boundary degradation facilitates a transition in crack growth mode from transgranular to intergranular, thereby accelerating crack propagation and exacerbating fatigue damage. Full article
(This article belongs to the Section Metals and Alloys)
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19 pages, 4331 KiB  
Article
Optimization of Grain Boundary Structure and Dielectric Properties in SrTiO3 Ceramics via Hot Isostatic Pressing
by Yilong Feng, Zhenya Lu, Ming Lv, Dan Qie and Zaiyun Long
Materials 2025, 18(14), 3301; https://doi.org/10.3390/ma18143301 - 13 Jul 2025
Viewed by 367
Abstract
This study fabricated SrTiO3 grain boundary layer ceramics using hot isostatic pressing (HIP), achieving a remarkably high dielectric constant of 60,350 and a superior breakdown strength of 1722 kV/m. Microstructural characterization via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed [...] Read more.
This study fabricated SrTiO3 grain boundary layer ceramics using hot isostatic pressing (HIP), achieving a remarkably high dielectric constant of 60,350 and a superior breakdown strength of 1722 kV/m. Microstructural characterization via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that HIP treatment significantly refined grain size uniformity and homogenized bismuth distribution at grain boundaries, thus enhancing the interfacial barrier effect. Probe-based impedance spectroscopy elucidated the dielectric behavior and conduction mechanisms of individual grain boundaries. HIP promotes the formation of interfacial barrier layers (IBLs), significantly improving electrical performance. Compared to untreated samples (average breakdown strength: 555 kV/m), HIP-processed ceramics exhibited a threefold enhancement in breakdown strength (1722 kV/m). The treated ceramic exhibited excellent temperature stability, with TCC ≤8% over −55 to 125 °C. The optimized dielectric properties stem from HIP-induced structural modifications, including reduced oxygen vacancy concentrations and homogenized electronic distribution at grain boundaries. These findings establish a quantitative correlation between HIP parameters, grain boundary restructuring, and macroscopic performance, providing critical insights for designing high-energy-density dielectric materials. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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19 pages, 2167 KiB  
Review
Grain Boundary Engineering for Reversible Zn Anodes in Rechargeable Aqueous Zn-Ion Batteries
by Yu-Xuan Liu, Jun-Zhe Wang, Lei Cao, Hao Wang, Zhen-Yu Cheng, Li-Feng Zhou and Tao Du
Metals 2025, 15(7), 784; https://doi.org/10.3390/met15070784 - 11 Jul 2025
Viewed by 338
Abstract
Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered significant research attention in the energy storage field owing to their inherent safety, cost-effectiveness, and environmental sustainability. Nevertheless, critical challenges associated with zinc anodes—including dendrite formation, hydrogen evolution corrosion, and mechanical degradation—substantially impede their practical implementation. [...] Read more.
Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered significant research attention in the energy storage field owing to their inherent safety, cost-effectiveness, and environmental sustainability. Nevertheless, critical challenges associated with zinc anodes—including dendrite formation, hydrogen evolution corrosion, and mechanical degradation—substantially impede their practical implementation. Grain boundary engineering (GBE) emerges as an innovative solution for zinc anode optimization through the precise regulation of grain boundary density, crystallographic orientation, and chemical states in metallic materials. This study comprehensively investigates the fundamental mechanisms and application prospects of GBE in zinc-based anodes, providing pivotal theoretical insights and technical methodologies for designing highly stable electrode architectures. The findings are expected to promote the development of aqueous zinc batteries toward a high energy density and long cycle life. Full article
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14 pages, 4026 KiB  
Article
Grain Refinement Caused by Dynamic Recrystallization Under Pulsed-Wave Laser Multi-Layer Cyclic Thermal Load
by Manping Cheng, Xi Zou, Yuan Zhu, Tengfei Chang, Qi Cao, Houlai Ju, Jiawei Ning, Yang Ding and Lijun Qiang
Coatings 2025, 15(7), 788; https://doi.org/10.3390/coatings15070788 - 3 Jul 2025
Viewed by 333
Abstract
In the Direct Energy Deposition (DED) process, the deposited material experiences intricate thermo-mechanical processes. Subsequent thermal cycling can trigger Dynamic Recrystallization (DRX) under suitable conditions, with specific strain and temperature parameters facilitating grain refinement and homogenization. While prior research has examined the impact [...] Read more.
In the Direct Energy Deposition (DED) process, the deposited material experiences intricate thermo-mechanical processes. Subsequent thermal cycling can trigger Dynamic Recrystallization (DRX) under suitable conditions, with specific strain and temperature parameters facilitating grain refinement and homogenization. While prior research has examined the impact of thermal cycling in continuous wave (CW) lasers on DRX in 316 L stainless steel deposits, this study delves into the effects of pulsed wave (PW) laser thermal cycling on DRX. Here, the thermo-mechanical response to PW cyclic thermal loading is empirically assessed, and the evolution of microstructure, grain morphology, geometric dislocation density (GND), and misorientation map during PW DED of 316 L stainless steel is scrutinized. Findings reveal that DRX is activated between the 8th and 44th thermal cycles, with temperatures fluctuating in the range of 680 K–750 K–640 K and grains evolving within a 5.6%–6.2%–5.2% strain range. After 90 thermal cycles, the grain microstructure undergoes significant alteration. Throughout the thermal cycling, dynamic recovery (DRV) occurs, marked by sub-grain formation and low-angle grain boundaries (LAGBs). Continuous dynamic recrystallization (CDRX) accompanies discontinuous dynamic recrystallization (DDRX), with LAGBs progressively converting into high-angle grain boundaries (HAGBs). Elevated temperatures and accumulated strain drive dislocation movement and entanglement, augmenting GND. The study also probes the influence of frequency and duty cycle on grain microstructure, finding that low pulse frequency spurs CDRX, high pulse frequency favors DRV, and the duty cycle has minimal impact on grain microstructure under PW cyclic thermal load. Full article
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20 pages, 6272 KiB  
Article
Experimental Investigation of the Interplay Between Al-, B-, and Ti-Nitrides in Microalloyed Steel and Thermodynamic Analysis
by Markus Führer, Sabine Zamberger, Christoph Seubert and Erwin Povoden-Karadeniz
Metals 2025, 15(7), 705; https://doi.org/10.3390/met15070705 - 25 Jun 2025
Viewed by 452
Abstract
Aluminum, boron, and titanium microalloyed into high-strength low-alloy boron steel exhibit a complex interplay, competing for nitrogen, with titanium demonstrating the highest affinity, followed by boron and aluminum. This competition affects the formation and distribution of nitrides, impacting the microstructure and mechanical properties [...] Read more.
Aluminum, boron, and titanium microalloyed into high-strength low-alloy boron steel exhibit a complex interplay, competing for nitrogen, with titanium demonstrating the highest affinity, followed by boron and aluminum. This competition affects the formation and distribution of nitrides, impacting the microstructure and mechanical properties of the steel. Titanium protects boron from forming BN and facilitates the nucleation of acicular ferrite, enhancing toughness. The segregation of boron to grain boundaries, rather than its precipitation as boron nitride, promotes the formation of martensite and thus the through-hardenability. Aluminum nitride is critical in controlling grain size through a pronounced pinning effect. In this study, we employ energy- and wavelength-dispersive X-ray spectroscopy and computer-aided particle analysis to analyze the phase content of 12 high-purity vacuum induction-melted samples. The primary objective of this study is to correctly describe the microstructural evolution in the Fe-Al-B-Ti-C-N system using the Calphad approach, with special emphasis on correctly predicting the dissolution temperatures of nitrides. A multicomponent database is constructed through the incorporation of available binary and ternary descriptions, employing the Calphad approach. The experimental findings regarding the solvus temperature of the involved nitrides are employed to validate the accuracy of the thermodynamic database. The findings offer a comprehensive understanding of the relative phase stabilities and the associated interplay among the involved elements Al, B, and Ti in the Fe-rich corner of the system. The type and size distribution of the stable nitrides in microalloyed steel have been demonstrated to exert a substantial influence on the properties of the material, thereby rendering accurate predictions of phase stabilities of considerable relevance. Full article
(This article belongs to the Special Issue Multi-scale Simulation of Metallic Materials (2nd Edition))
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14 pages, 3540 KiB  
Article
Effects of In Situ Electrical Pulse Treatment on the Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy Resistance Spot Welds
by Shitian Wei, Xiaoyu Ma, Jiarui Xie, Yali Xie and Yu Zhang
Metals 2025, 15(7), 703; https://doi.org/10.3390/met15070703 - 24 Jun 2025
Viewed by 304
Abstract
This study introduces a novel in situ pulsed current-assisted resistance spot welding method, which differs fundamentally from conventional post-weld heat treatments and is designed to enhance the mechanical performance of 7075-T651 aluminum alloy joints. Immediately after welding, a short-duration pulsed current is applied [...] Read more.
This study introduces a novel in situ pulsed current-assisted resistance spot welding method, which differs fundamentally from conventional post-weld heat treatments and is designed to enhance the mechanical performance of 7075-T651 aluminum alloy joints. Immediately after welding, a short-duration pulsed current is applied while the weld remains in a high excess-vacancy state, effectively accelerating precipitation reactions within the weld region. Transmission electron microscopy (TEM) observations reveal that pulsed current treatment promotes the formation of band-like solute clusters, indicating a significant acceleration of the early-stage precipitation process. Interestingly, the formation of quasicrystalline phases—rare in Al-Zn-Mg-Cu alloy systems—is incidentally observed at grain boundaries, exhibiting characteristic fivefold symmetry. Selected area electron diffraction (SAED) patterns further show that these quasicrystals undergo partial dissolution under the influence of the pulsed current, transforming into short-range ordered cluster-like structures. Lap shear tests demonstrate that joints treated with pulsed current exhibit significantly higher peak load and energy absorption compared to untreated specimens. Statistical analysis of weld size confirms that both groups possess comparable weld diameters under identical welding currents, suggesting that the observed mechanical improvements are primarily attributed to microstructural evolution rather than geometric factors. Full article
(This article belongs to the Special Issue Welding and Fatigue of Metallic Materials)
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22 pages, 4820 KiB  
Article
Microstructure and Properties of Corrosion-Resistant Steel Produced by CASTRIP
by Kai Lei, Long Chen, Hengchang Lu, Xintong Lian, Qingxiao Feng, Hualong Li and Han Dong
Crystals 2025, 15(7), 595; https://doi.org/10.3390/cryst15070595 - 24 Jun 2025
Viewed by 397
Abstract
The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant [...] Read more.
The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant steel was produced through the CASTRIP process. Microstructure and properties were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal microscopy (LSCM), electron backscattered diffraction (EBSD), and tensile testing. The results show that the microstructure is mainly composed of polygonal ferrite, bainite ferrite, and acicular ferrite. The bainite ferrite forms parallel lath bundles nucleating at austenite grain boundaries, propagating perpendicularly into the parent grains. The acicular ferrite exhibits a cross-interlocked morphology preferentially nucleating at oxide/sulfide inclusions. Microstructural characterization confirms that the phase transformation of acicular ferrite and bainite ferrite introduces high-density dislocations, identified as the primary strengthening mechanism. Under the CASTRIP process, corrosion-resistant elements such as Cu, P, Sb, and Nb are completely dissolved in the matrix without grain boundary segregation, thereby contributing to solid solution strengthening. Full article
(This article belongs to the Special Issue Phase Transformation and Microstructure Evolution of Alloys)
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13 pages, 3556 KiB  
Article
High-Temperature Tensile Grain Evolution and Mechanical Properties of Additively Manufactured TA15 Aerospace Titanium Alloy
by Pengfei Li, Zhenkun Dong, Qingtao Yang, Hao Xu, Dehai Kong and Minghui Hu
Metals 2025, 15(6), 677; https://doi.org/10.3390/met15060677 - 18 Jun 2025
Cited by 1 | Viewed by 355
Abstract
This study investigates the grain characteristics and high-temperature tensile properties of an additively manufactured (AM) TA15 titanium alloy. Directed energy deposition (DED) was utilized for its high material efficiency and design flexibility to explore the alloy’s applicability in aerospace manufacturing, where TA15 is [...] Read more.
This study investigates the grain characteristics and high-temperature tensile properties of an additively manufactured (AM) TA15 titanium alloy. Directed energy deposition (DED) was utilized for its high material efficiency and design flexibility to explore the alloy’s applicability in aerospace manufacturing, where TA15 is valued for its excellent high-temperature performance. A comparative analysis between DED and hot-rolled TA15 alloys was conducted at 25 °C and 600 °C to examine the influence of grain size and crystallographic texture on mechanical behavior. The AM TA15 alloy exhibited superior tensile properties at both temperatures compared to its hot-rolled counterpart. Microstructural analysis revealed finer grain size, stronger α-phase diffraction intensity, and altered grain boundary misorientation in the AM alloy after high-temperature testing, accompanied by improved plasticity. These findings highlight the potential of thermal process optimization and microstructural tailoring to enhance the high-temperature performance of AM TA15, offering valuable insights for the fabrication of critical aerospace components. Full article
(This article belongs to the Special Issue Machining, Grinding, and Laser Processing of Metallic Materials)
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15 pages, 1470 KiB  
Article
Multiscale Modeling and Analysis of Hydrogen-Enhanced Decohesion Across Block Boundaries in Low-Carbon Lath Martensite
by Ivaylo H. Katzarov
Metals 2025, 15(6), 660; https://doi.org/10.3390/met15060660 - 13 Jun 2025
Viewed by 382
Abstract
Low-carbon lath martensite is highly susceptible to hydrogen embrittlement due to the presence of a high density of lath/block boundaries. In this study, I employ a continuum decohesion model to investigate the effects of varying hydrogen concentrations and tensile loads on the cohesive [...] Read more.
Low-carbon lath martensite is highly susceptible to hydrogen embrittlement due to the presence of a high density of lath/block boundaries. In this study, I employ a continuum decohesion model to investigate the effects of varying hydrogen concentrations and tensile loads on the cohesive strength of low- and high-angle block boundaries. The thermodynamic properties of the cohesive zone are described using excess variables, which establish a link between atomistic energy calculations and the continuum model for gradual decohesion at a grain boundary. The aim of this study is to develop an in-depth understanding of how hydrogen affects the cohesive strength of block boundaries in a lath martensitic structure by integrating continuum and atomistic computational modeling and to apply the resulting insights to investigate the effects of varying hydrogen concentrations and tensile loads on interface decohesion. I incorporate hydrogen mobility and segregation at low- and high-angle twist boundaries in body-centered cubic (bcc) Fe to quantify the hydrogen-induced effects on progressive decohesion under tensile stress. A constant hydrogen flux through the free surfaces of a bicrystal containing a block boundary is imposed to simulate realistic boundary conditions. The results of the simulations show that, in the presence of hydrogen flux, separation across the block boundaries occurs at a tensile load significantly lower than the critical stress required for rupture in a hydrogen-free lath martensitic structure. Full article
(This article belongs to the Special Issue Hydrogen Embrittlement of Metals: Behaviors and Mechanisms)
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17 pages, 9797 KiB  
Article
An Investigation into the Thermomechanical Processing and Dynamic Recrystallization Mechanisms of High-Magnesium Aluminum Alloys
by Zili Ye, Zixiao Zhou, Zhaolin Ye, Zhi Wang, Qizhong Zhao and Konda Gokuldoss Prashanth
Materials 2025, 18(12), 2734; https://doi.org/10.3390/ma18122734 - 11 Jun 2025
Viewed by 489
Abstract
In this study, we studied the dual role of magnesium on the high-temperature deformation mechanisms and microstructural evolution of high-Mg 5383 aluminum alloys. We developed a quantitative framework to characterize high-temperature flow behavior and constructed 3D processing maps to identify processing instabilities. The [...] Read more.
In this study, we studied the dual role of magnesium on the high-temperature deformation mechanisms and microstructural evolution of high-Mg 5383 aluminum alloys. We developed a quantitative framework to characterize high-temperature flow behavior and constructed 3D processing maps to identify processing instabilities. The results indicate that solid solution strengthening induced by Mg atoms leads to a substantial increase in peak flow stress. The thermal activation energy rises significantly from 182 kJ/mol to 209 kJ/mol at a Mg content of 5 wt.%, which highlights the pronounced solute drag effects on dislocations. Moreover, Mg-modified grain boundary dynamics enhance power dissipation efficiency by 34% (from 35% to 47%). With an increasing Mg content, the processing instability domains expand, thereby shifting the optimal processing parameters towards higher-temperature and lower-strain-rate regions (500 °C/0.05 s−1). The results provide a theoretical foundation for optimizing the thermal processing characteristics and mechanical properties of high-Mg aluminum 5xxx series alloys. Full article
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