The low density of Mg alloys makes them advantageous in lightweight structures for transportation, reducing energy costs and CO2 emissions. However, the production of Mg alloys is energy intensive and produces large amounts of waste, weakening the advantage of Mg alloys as a green material. A solid-state recycling method incorporating spark plasma sintering (SPS) and friction stir processing (FSP) has been proposed to recycle Mg-Y-RE alloy scraps produced during the machining process. In the first step, SPS rapidly turned scraps into a consolidated disk, with coarse grains, second phases and large pores. In the following FSP step, dynamic recrystallisation refined grains to about 1.2-3.0 mu m. Large second phases were partly re-dissolved into the matrix and redistributed. Pore size and fraction were reduced and a more densified disk was then obtained. The FSPed disk exhibited a yield strength (YS) of 190.3 MPa and an elongation (El) of 3.8%. Further ageing increased the YS to 226.5 MPa, whilst decreasing the El to 2.2%. The mechanical properties of the recycled material are comparable to cast and additively manufactured counterparts. It offers a possibility of the combination use of powder metallurgy and plastic deformation to achieve solid-state recycling of Mg alloys.

Infection remains a major cause of implant failure, motivating the development of biodegradable metals with intrinsic antibacterial activity. This study investigated how minor silver (Ag) addition regulates the degradation and antibacterial performance of extruded Mg-2Zn-0.2Ca alloys. Adding 0.1 wt % Ag significantly reduced the degradation rate to 0.14 ± 0.04 mm/y after 672 h of immersion, lower than WE43 (0.66 ± 0.05 mm/y), whereas higher Ag contents accelerated degradation. Extracts from the Ag-free alloy showed moderate antibacterial rates of 43.4% ± 0.06% and 62.4% ± 3.55% against Escherichia coli and Staphylococcus aureus, respectively. With 0.1 wt % Ag, these rates increased significantly to 83.4% ± 3.82% and 92.1% ± 2.66%, comparable to WE43. Adenosine triphosphate assays, reactive oxygen species detection, and electron paramagnetic resonance analysis indicated that the enhanced antibacterial activity of Ag-containing alloys involved adenosine triphosphate depletion and oxidative stress. Overall, ZXQ0.1 represents a promising candidate for further investigation as a biodegradable antimicrobial magnesium alloy.

Unexpectedly, huge cracks were observed at grain boundaries (GBs) during laser-directed energy deposition of high-strength and high-toughness CoCrNi medium-entropy alloy. To accurately analyze crack formation mechanism, GBs energy was calculated by first-principles methods. The results revealed that O tends to accumulate at GBs and reduce GBs strength, resulting in crack initiation and propagation. Consequently, crack inhibition is achieved through reduction of O content in additively manufacturing CoCrNi and incorporation of TiAl alloy powder. To elucidate the suppression mechanism, computation of adsorption energy between CoCrNi and TiAl suggests that O preferentially combines with TiAl to form nano-precipitates, decreasing the formation of crack.

Grain growth governs the strength, ductility and creep performance of metals, yet spatial heterogeneity and mechanisms of abnormal grain growth (AGG) remain debated. We coupled 4D LabDCT with our newly developed grain-tracking toolbox (Track-4DGG) to investigate grain growth in a WE43 Mg alloy during interrupted annealing. The grain feature evolution can be extracted from the tracking results, at both individual grain and grain cluster scales. We observe pronounced spatial differences in growth kinetics, with the surface section suppressing normal coarsening but promoting AGG rates. Contrarily, the inner section contains more AGG occurrences but with lower growth rates. More than 50% of the grains within two grain diameters of the initial surface are consumed, and the surviving grains are larger than their interior counterparts. This divergence in growth kinetics is attributed to a ring-like second-phase free band (SPFB) forming towards the surface during annealing.

Additive friction stir deposition (AFSD), as a solid-state-additive manufacturing technique with a high deposition rate, provides an innovative route for fabricating high-performance magnesium (Mg) alloys while avoiding solidification defects. In this study, the effects of T6 heat treatment on the microstructure, mechanical properties, and deformation mechanisms of an AFSD Mg-9Gd-3Y-0.5Zr (wt.%) alloy were systematically investigated. The AFSD alloy exhibited a heterogeneous onion-ring microstructure composed of alternating fine grains (similar to 3.9 mu m) enriched with nanoscale cuboid Mg-24(Gd, Y)(5) precipitates and coarse grains (similar to 10.6 mu m) containing limited precipitates, which originated from the non-uniform precipitate distribution in the feedstock. The T6 heat treatment eliminated dislocation structures, introduced abundant nano-Mg-7(Gd, Y) (beta ') precipitates and coarsened the fine and coarse grains to similar to 7.3 and similar to 67.4 mu m, respectively. Consequently, the AFSD and AFSD-T6 alloys achieved superior strength-ductility combinations compared to the feedstock, with yield strength/ultimate tensile strength/elongation of 293.5 MPa/330.3 MPa/8.1% and 366.8 MPa/374.3 MPa/5.1%, respectively. The heterogeneous grains induced pronounced hetero-deformation-induced hardening in both conditions, while basal < a > slip activity was progressively enhanced during deformation. However, extensive twinning, particularly double twinning in the coarse grains of the AFSD-T6 alloy, led to reduced ductility. Overall, this work demonstrates that coupling AFSD with tailored heat treatment enables effective microstructural heterogeneity engineering, offering a robust strategy for developing Mg-Gd-Y-Zr alloys with outstanding mechanical performance. (c) 2026 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

The interaction between dislocations and deformation twins strongly influences microstructural evolution and deformation behavior in Mg alloys. In this work, the effects of dislocation-twin interactions on twinning and slip behavior in AZ31 magnesium (Mg) alloy were investigated using a two-step quasi-in-situ compression approach. The results show that during the initial deformation stage, basal-prismatic/prismatic-basal (BP/PB) interfaces generated by dislocation-twin interactions suppress twin growth while promoting new twin nucleation and non-basal dislocation transformation, with the strongest pinning effect occurring at an intermediate interface density. During subsequent deformation, twin growth continues, while dislocation slip gradually becomes the predominant deformation mode. Basal ⟨a⟩ dislocations transform into non-basal dislocation types through distinct pathways governed by geometric compatibility. Direct transformation is favored at high geometric compatibility factor (m′), whereas indirect transformation predominates at low m′ values. These findings reveal how BP/PB interfaces influence twin evolution and dislocation transformation in Mg alloys.

Current crystallographic analyses of bainitic transformation are largely constrained by uncertainties in prior austenite orientation reconstruction and the inherent limitations of post-mortem microstructures. In this work, in-situ high-temperature EBSD dataset was employed to track crystallographic evolution of bainite under continuous cooling. Previously unreported characteristics, which also cannot be captured by conventional postmortem analysis, were revealed. The results show that orientation relationships (ORs) exhibit a clear temperature dependence, with both the deviation angles of the close-packed planes and close-packed directions initially increasing and then reaching a plateau. Variant pairing undergoes a three-stage evolution, transitioning from being predominantly within the same CP (close-packed) group to coexisting in multiple variant pairs as the transformation temperature decreases. The heterogeneity in transformation sequences and crystallographic features, as well as the preferential nucleation of bainite at twin boundaries, were also confirmed experimentally. This study not only provides guidance for designing steel cooling processes and tailoring bainite microstructure, but also establishes a quantitative framework for in-situ high-temperature EBSD analysis.

Next-generation H2-powered aircraft store their fuel as liquid, necessitating on-board storage and transportation systems to operate at -253°C (liquid H2 boiling point). These systems need to be lightweight, strong, and most importantly, ductile in cryogenic conditions. Al alloys are well-suited for this; however, conventional manufacturing processes require welded joints that potentially act as failure points, especially under extreme cryogenic conditions. A jointless design is therefore preferred, and additive friction stir deposition (AFSD) offers a promising solution. However, precipitation-hardened Al alloys typically lose their strength drastically after AFSD due to precipitate coarsening and redissolution. In this study, cryogenic quenching was introduced, and the subsequent aging conditions were varied to tailor the cryogenic mechanical performance, resulting in a 3D printed component with strength comparable to the original base material Al 6082-T6 but with 97% greater ductility at -253 °C.

Annealing is widely applied to the deformed magnesium alloys to tailor crystallographic texture and improve formability, significant efforts have been made to understand recrystallisation nucleation and grain growth. Nevertheless, it is still a highly debated field, attributes to the lack of large area in-situ microstructure datasets and effective data processing approach, especially the grains tracking strategy. In this work, the recrystallisation process of a Mg-2.4Zn-0.2Ce wt% alloy is systematically investigated with quasi-in-situ electron backscatter diffraction method to unravel the role of shear bands during recrystallisation annealing. A newly developed toolbox Track-Rex is adopted, allowing us to automatically track 40,900 grains within 10 min. The results show that shear bands were the preferential nucleation sites at early stage of annealing. However, with increased annealing time, the preferred nucleation sites shifted to the deformed grain boundaries, and the grains nucleated from shear bands were progressively consumed. Thus, the contribution of shear bands induced nucleation to the recrystallised texture is considerably reduced, from up to 51.2 % of area fraction in the early stage towards 20.89 % in the final annealing stage. In terms of texture evolution, all the recrystallised grains exhibit a scattered off- basal feature regardless to the nucleation sites. Additionally, the basal orientated grains were gradually consumed while off-basal grains had a higher possibility to retained. More specifically, within shear bands induced nucleation, recrystallised grains with low angle grain boundaries were easily consumed, while other grains exhibiting high angle grain boundaries were more likely to maintain along the recrystallisation procedure.

This work investigates the influence of Mg–Zn–Ca alloy compositions and rapid cooling conditions on microstructural evolution, with a focus on the formation and behaviour of intermetallic phases such as Mg 2 Ca, MgZn, and Ca 2 Mg 6 Zn 3 during solidification. To achieve this, a combination of experimental characterisation and computational modelling was employed. The Scheil model, extended to ternary alloy systems, was used to simulate micro-segregation during solidification, while a multicomponent mean-field model was applied to predict solid-state phase transformations and the evolution of second-phase particles. CALPHAD-based thermodynamic calculations were integrated to refine the prediction of segregation pathways and phase distributions under non-equilibrium conditions. The model successfully differentiates solidification paths based on alloy composition, predicting that Mg–0.8Zn–0.2Ca (wt%) first forms Mg 2 Ca phase segregation, whereas Mg–6.8Zn–0.2Ca (wt%) primarily segregates MgZn. Experimental validation using SEM–EDS characterisation confirms these predictions. Finally, intermetallic phase formation diagrams under different solidification conditions are presented, providing insights into the control of intermetallic phase formation in Mg–Zn–Ca alloys.

It is generally believed that the addition of rare earth (RE) elements can modify the texture distribution to form a distinct RE texture, which is typically weaker and more dispersed than conventional textures. In this study, we systematically investigated the influence of extrusion temperature and speed synergy on grain boundary segregation and texture evolution in Mg-2Zn-1Gd (wt.%) alloy. Further investigation using Electron Backscattered Diffraction (EBSD) and Energy Dispersive Spectroscopy (EDS) in Scanning transmission electron microscopy mode (STEM-EDS) revealed that rare earth magnesium alloys (Mg-RE alloys) do not invariably result in the formation of RE textures, that is under low-temperature and low-speed conditions, Zn/Gd co-segregation dominates RE texture formation by increasing the critical strain for dynamic recrystallization and promoting the nucleation of twins and shear bands. Under high-temperature and high-speed conditions, an imbalance in segregation kinetics (grain boundary migration rate > solute diffusion rate) activates basal slip. This basal slip is activated within recrystallized grains to accommodate imposed strain, contributing to the development of a strong basal texture. In addition, the effect of microstructure evolution with extrusion parameters on mechanical properties of Mg-2Zn-1Gd rods are also systematically investigated, and a numerical calculation are conducted to determine the mechanism on the effect of texture evolution on mechanical properties.

High-throughput methods can accelerate the development of metal alloys and (nano)composites, both empirically and as input to computational methods. This study introduces a new route to fabricating composite wires with longitudinally varying composition using the byproduct of stationary-shoulder friction stir channelling (SS-FSC); this sample format is attractive for a variety of rapid read-out options in the future. The concept is illustrated by preparing Mg composite wires with a longitudinally graded concentration of SiC-particles. Spark plasma sintering (SPS) was used to encode a step-change in SiC concentration within a feedstock billet. Subsequent SS-FSC transformed this discrete compositional step into a continuous, graded extruded wire. Micro-structural analysis revealed significant grain refinement from the SPS billet (44.3 f 2.3 mu m) to the SS-FSC wire (7.4 f 0.5 mu m), with even finer grains in SiC-loaded regions (5.1 f 0.5 mu m), attributed to particle-stimulated nucleation. Mechanical characterisation confirmed a hardness increase, from 65.8 f 1.2 HV3 to 68.9 f 2.7 HV3 (high SiC-content). This proof-of-concept study confirms the effectiveness of SS-FSC in producing high-quality wires with tailored microstructural and mechanical gradients. Additional compositions could be readily multiplexed in the original billet, providing a robust high-throughput technique for comprehensive structure-property investigations of advanced alloys and composites.

Producing steel requires large amounts of energy to convert iron ores into steel, which often comes from fossil fuels, leading to carbon emissions and other pollutants. Increasing scrap usage emerges as one of the most effective strategies for addressing these issues. However, typical residual elements (Cu, As, Sn, Sb, Bi, etc.) inherited from scrap could significantly influence the mechanical properties of steel. In this work, we investigate the effects of residual elements on the microstructure evolution and mechanical properties of a quenching and partitioning (Q&P) steel by comparing a commercial QP1180 steel (referred to as QP) to the one containing typical residual elements (Cu+As+Sn+Sb+Bi<0.3wt%) (referred to as QP-R). The results demonstrate that in comparison with the QP steel, the residual elements significantly refine the prior austenite grain (9.7 mu m vs. 14.6 mu m) due to their strong solute drag effect, leading to a higher volume fraction (13.0 % vs. 11.8 %), a smaller size (473 nm vs. 790 nm) and a higher average carbon content (1.26 wt% vs. 0.99 wt%) of retained austenite in the QP-R steel. As a result, the QP-R steel exhibits a sustained transformation-induced plasticity (TRIP) effect, leading to an enhanced strain hardening effect and a simultaneous improvement of strength and ductility. Grain boundary segregation of residual elements was not observed at prior austenite grain boundaries in the QP-R steel, primarily due to continuous interface migration during austenitization. This study demonstrates that the residual elements with concentrations comparable to that in scrap result in significant microstructural refinement, causing retained austenite with relatively higher stability and thus offering promising mechanical properties and potential applications. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Aluminium alloys, celebrated for their high strength-to-weight ratio and remarkable tensile strength in lightweight structural applications, are integral to a broad spectrum of industries. In this work, we proposed a precipitation strengthening model incorporating the competitive relationship between nucleation and growth to optimise composition, and developed an age-hardenable Al-4.2Mg-0.7Mn-1.1Sc-0.5Zr-0.6Cu-0.1Zn-0.1Fe (wt.%) alloy for laser powder bed fusion. This alloy features a hierarchically heterogeneous microstructure with a trimodal grain and nanoprecipitate distribution. It undergoes the nucleation and growth of secondary Al3X precipitates and the subsequent dissolution of the S-phase, with a significant number of T-phase observed by atom probe tomography. This combined multi-precipitate structure results in a maximum yield strength of 650 MPa displaying a high work hardening rate, making it a promising candidate for complex-shaped, high-strength and ductile components in advanced light-weight structural engineering applications. The new modelling approach to control nanoprecipitation nucleation and growth aids in realising the potential for near-net shape forming of Al alloy components.

This paper investigates a new 'forged' wire additive manufacturing processing, in which the metal wire is produced as a by-product from stationary shoulder friction stir channelling (SS-FSC) under the severe plastic deformation mechanism (known as CoreFlow (R)), and then used as the feedstock in directed energy deposition with a laser beam and wire feedstock (DED-LB/w) additive manufacturing. For the first time, the 'by-products' produced in the SS-FSC process, which are 'forged' 6082 aluminium alloy wire, were tested with built-tracks using DED-LB/w. Process mapping was built to demarcate the melting states, including the stable, dripping, and incomplete melting regimes, over a wide range of laser energy densities (92 to 303 kJ center dot s center dot g-1 center dot cm-2). Metallurgy tests were also conducted to reveal the evolution of the microstructure and defect formation of the deposited tracks. It was found that: (i) Stable deposition with a grain size of 9-20 mu m can be achieved with optimised processing parameters, i.e., energy density 243 kJ center dot s center dot g-1 center dot cm-2 with a laser power 3.8 kW, a scanning speed 0.8 cm center dot s-1 and a wire feed rate 2.0 cm center dot s-1; (ii) The substructure morphology is gradually transitioned from columnar at the track bottom to cellular (8.9 +/- 1.8 mu m) at the top, driven by an increased cooling rate; and (iii) The built track porosity is mainly composed of gas pores that are small (equivalent diameter of 20-50 mu m) and spherical, primarily resulting from the ambient gas, the SS-FSC extruded wire oxides and contaminations. The study supports resource-efficient, low-carbon manufacturing via reuse of by-products, in alignment with the Net Zero Strategy.

Additive ManufacturingAdditive manufacturing (AM) is crucial for Industry 4.0Industry 4.0 where automation and real-time decision-making are to be performed with minimal human intervention. Most AM techniques involve meltingMelting metal powders layer-by-layer to build components which allows for complex geometries to be achieved; however, some challenges that inhibit it from becoming mainstream are hot cracking, porosity produced in the specimens, anisotropy and heterogeneity in the components with respect to the microstructureMicrostructure, mechanical propertiesMechanical properties, and crystallographic textureTexture. Such problems could be overcome if AM is performed without meltingMelting. In this regard, additive friction stir deposition (AFSD) exhibits the highest potential for industrialization. AFSD involves depositing a solid metal feedstock bar layer-by-layer while being heated by a rotating tool. In this work, the process, microstructureMicrostructure, crystallographic textureTexture, and hardnessHardness of Al 60826082 alloyAlloys after AFSD have been investigated. A fine-grained microstructureMicrostructure was obtained. However, there was a reduction in the hardnessHardness by 54

The anisotropy properties of samples in different direction is found in additively manufactured (AM) CoCrNi medium-entropy alloys (MEAs). In this study, the laser direct energy deposition AM CoCrNi MEAs have been subjected to two alternative processing methods: hot isostatic pressing (HIP) and ultrasonic impact treatment (UIT). The effect of HIP and UIT on the microstructure, grain orientation, grain boundary distribution, phase distribution and mechanical properties of AM CoCrNi MEAs were systematically studied. The results show that HIP decreased the partial mechanical anisotropy of AM CoCrNi MEAs, and YS was significantly reduced. The main reason is that the HIP induces the formation of large number of Cr2O3 particles, and transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs). Surprisingly, both the yield strength (YS) and ultimate tensile strength (UTS) of the AM CoCrNi MEAs were increased when the UIT was added after every laser deposition of one layer (UIT-1). This is due to the combined effect of quasi-static loading and ultrasonic oscillations of UIT, which results in the dislocation multiplication and the formation of a large number of substructures. In addition, the above strengthening phenomena also lead to decrease partial mechanical anisotropy of AM CoCrNi MEAs.

In this study, the microstructure, mechanical properties, and thermal conductivity of as-extruded Mg-4Zn-0.6Zr-xCa (x = 0, 0.3, 0.6, 0.9 wt.%) alloys were investigated. The results revealed a bimodal grain size distribution in all the alloys due to incomplete dynamic recrystallization (DRX), characterized by the coexistence of elongated deformed grains and equiaxed DRX grains. The bimodal grain size distribution enhanced the mechanical properties of the studied alloys. Furthermore, Ca alloying facilitated the formation of Ca2Mg6Zn3 phases, through which the DRX extent was also enhanced. The precipitation of secondary phases, along with the increased DRX induced by Ca addition, was beneficial in eliminating the lattice distortion of the alloys, resulting in improved thermal conductivity compared to the Ca-free Mg-4Zn-0.6Zr alloy. The optimum combination of mechanical properties and thermal conductivity was achieved in the Mg-4Zn-0.6Zr-0.6Ca alloy, with yielding strength, ultimate tensile strength, tensile fracture elongation, and thermal conductivity values of 271 MPa, 318 MPa, 17.6%, and 123.9 W/(m‧K), respectively. This work demonstrates that Mg-Zn-Zr-Ca-based alloys can be developed with high strength and high thermal conductivity, significantly expanding the industrial application of magnesium alloys.

The present work investigates effects of micro-alloying Ag on the microstructure, mechanical properties and corrosion behavior of as-extruded Mg-2Zn-0.2Ca alloys. The addition of Ag, up to 0.5wt.%, induce limited difference on microstructural characteristics such as slightly coarser microstructures due to the enhanced dynamic recrystallization process and the presence of refined precipitates. The tensile properties of the alloy were not significantly changed by Ag addition, i.e., all the alloys exhibited exceptional elongation of ~30%, moderate tensile yield strength and ultimate strength of ~140MPa and ~240MPa, respectively. The corrosion performance of the alloys was progressively deteriorated with increasing Ag content i.e., the corrosion rate increased from 0.40 ± 0.23mm/y for Mg-2Zn-0.2Ca alloy to 3.27 ± 0.24mm/y for the Mg-2Zn-0.2Ca-0.5Ag alloy. The compromised corrosion performance was attributed to a large electrode potential difference between the nobler Ca2Mg6Zn3 phase and the α-Mg matrix as well as a less protective corrosion film, by increasing Ag addition.

Additively manufactured (CoCrNi)94(TiAl)6 medium -entropy alloys (MEAs) were fabricated by laser -directed energy deposition. The strengthening induction mechanism in the additively manufactured (CoCrNi)94(TiAl)6 MEAs was investigated using electron backscatter diffraction and transmission electron microscopy. The results showed that the addition of TiAl powder led to increases of 29.6% and 43.5% in the ultimate tensile strength (UTS) and yield strength (YS), respectively, at 298 K, and a decrease of 17.1% in the elongation. For the samples tested at 77 k after the addition of the TiAl powder, the UTS and YS improved by 26.6% and 28.0%, respectively, and the elongation increased by 26.3%. The microstructural observation results indicated that the matrix grains changed from initial columnar grains with a uniform growth direction to fine dendrites. Numerous TiO clad Al2O3 strengthening nano -precipitates with a novel core-shell structure were found in the additively manufactured (CoCrNi)94(TiAl)6 MEAs, and both featured a face -centered cubic structure. No crystallographic orientation was observed between the nano -precipitates and the matrix. At 298 K, the dislocation line bypassed the nanoprecipitates during the plastic deformation period and Lomer-Cottrell locks appeared near the nanoprecipitates, thereby strengthening the additively manufactured (CoCrNi)94(TiAl)6 MEAs. At 77 K, plastic deformation resulted in the synergistic deformation of the nano -precipitates and matrix, the formation of a large number of dislocations, and a twinning induced plasticity effect, which further increased the strength and plasticity of the additively manufactured (CoCrNi)94(TiAl)6 MEAs.