Search Results (3,651)

Wire Arc Additive Manufacturing (WAAM) is a cost-effective method for fabricating large aluminum components; however, it tends to suffer from heat accumulation and coarse anisotropic microstructures, which can limit the part’s performance. In this study, a wall is fabricated using a hybrid unified additive deformation manufacturing process (UAMFSP) method, which integrates friction stir processing (FSP) into WAAM, and is compared with a Metal Inert Gas (MIG)-based WAAM wall. Infrared (IR) thermography revealed progressive heat buildup in MIG walls, with peak layer temperatures of about 870 to 1000 °C. In contrast, in the UAMFSP process, heat was redistributed through mechanical stirring, maintaining more uniform sub-solidus profiles below approximately 400 °C. Also, optical microscopy and quantitative image analysis showed that MIG walls developed coarse, dendritic grains with a mean grain area of about 314 µm², whereas the UAMFSP produced refined, equiaxed grains with a mean grain area of about 10.9 µm². Microhardness measurement (Vickers HV0.2, 200 gf) confirmed that the UAMFSP process can improve the hardness by 45.8% compared to the MIG process (75.8 ± 7.7 HV vs. 52.0 ± 1.3 HV; p = 0.0027). In summary, the outcomes of this study introduce the UAMFSP process as a method for addressing the thermal and microstructural limitations of WAAM. These findings provide a framework for further extending hybrid additive–deformation strategies to thicker builds, alternative alloys, and service-relevant mechanical evaluations. Full article

The ductile shear zones in northern Guangxi provide a crucial window for understanding Paleozoic collisional deformation and the tectonic evolution of the South China Block. The Jiufeng–Gandong ductile shear zone is located in the western part of the Motianling pluton in northern Guangxi. The penetrative mylonitic foliation within the ductile zone dips toward the ESE at angles of 55°–85°. Kinematic analyses indicate that the Jiufeng–Gandong ductile shear zone experienced sinistral thrust shearing. Anisotropy of magnetic susceptibility (AMS) results show that the shear zone generally strikes in an NNE direction, with a length exceeding 30 km and a maximum width of more than 2.5 km. The flattening degree (E value) of the magnetic susceptibility ellipsoid suggests that deformation within the shear zone is dominated by flattening strain, accompanied by a component of extensional strain. Quartz dynamic recrystallization mechanisms and electron backscatter diffraction (EBSD) analyses indicate that the sinistral thrust shearing occurred at deformation temperatures of approximately 350–650 °C. LA–ICP–MS U–Pb dating of zircons from a mafic mylonite yields a crystallization age of 443.0 ± 2.8 Ma. By integrating macro- and microstructural observations, magnetic fabric data, quartz EBSD fabric analyses, regional published geochronological constraints, and hydrothermal zircon U–Pb ages obtained in this study, we propose that the Jiufeng–Gandong ductile shear zone developed during Caledonian thrusting of the Cathaysia Block onto the Yangtze Block from SE to NW. Under collisional compression, the shear zone underwent medium- to high-temperature sinistral thrust shearing accompanied by dominant flattening strain. These results elucidate the geometry, strain characteristics, and tectonic regime of the Jiufeng–Gandong ductile shear zone, providing new insights into the Caledonian tectonic evolution of South China. Full article

As a solid-state joining technology, friction stir welding (FSW) exhibits significant advantages for joining aluminium alloys, including low heat input and minimal formation of intermetallic compounds, thereby enhancing joint quality and mitigating deformation. This study investigates the single-sided and double-sided FSW processes of 3 mm thick 7075-T6 aluminium alloy sheets, focusing on characterising the microstructure and mechanical properties of the joints. Experimental results show that at a rotational speed of 1500 rpm and a welding speed of 80 mm/min, the double-sided co-directional FSW joint achieves a tensile strength of 388 MPa and an elongation of 7.09%, significantly outperforming those of the other two welding paths. In the weld nugget zone (WNZ), continuous dynamic recrystallization (CDRX) occurs, generating uniformly refined equiaxed grains (average size: 1.10 μm) and facilitating the transformation of low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs). Meanwhile, the strong rotated cube texture is remarkably weakened and replaced by random recrystallized brass textures with the lowest kernel average misorientation (KAM) value in the WNZ. In contrast, the thermo-mechanically affected zone (TMAZ) accumulates a high density of LAGBs due to welding-induced plastic deformation. Microhardness testing reveals a typical “W”-shaped distribution: WNZ hardness is relatively high but slightly lower than that of the base metal (BM), and the minimum hardness of the advancing side (AS) of the heat-affected zone (HAZ) is higher than that of the retreating side (RS). This study confirms that double-sided co-directional FSW crucially regulates microstructural evolution and improves the mechanical properties of 7075-T6 aluminium alloy joints, providing a viable process optimisation strategy for high-quality welding of thin-gauge sheets. Full article

This study examines the mechanical response of medium-manganese TRIP steels under different stress states, focusing on deformation-induced austenite-to-martensite transformation and ageing phenomena. Two steels with distinctly different ferrite–austenite morphologies and retained austenite (RA) fractions were analysed: a globular microstructure with 18% RA and a lamellar microstructure with 14% RA, produced by single (SA) and double annealing (DA), respectively. Continuous and interrupted tests were performed under in-plane shear, uniaxial tension, and plane strain stress states. Strain fields were analysed using high-resolution digital image correlation, while RA fractions were quantified as a function of strain by ex situ X-ray diffraction. The results demonstrate a pronounced stress-state dependence. SA samples exhibit discontinuous yielding, with uniaxial tests showing clear Lüders band formation. Both steels exhibit dynamic strain ageing manifested by Portevin–Le Chatelier (PLC) serrations and associated strain bands, which are most pronounced under uniaxial tension, weaker in plane strain, and barely detectable in in-plane shear. Static strain ageing is also evidenced by a strengthened yield response upon unloading–reloading in all samples. The SA globular microstructure exhibits higher PLC band inclination angles than the lamellar DA microstructure, consistent with its more pronounced anisotropy. The propagation velocity in uniaxial tensile samples decreases with increasing strain following the work-hardening response. For both steels, the austenite-to-martensite transformation rate is highest in uniaxial tension, slightly reduced in plane strain, and strongly suppressed under in-plane shear. A Beese–Mohr/Johnson–Mehl–Avrami–Kolmogorov formulation incorporating stress triaxiality and Lode angle captures these trends for both steels. For the stress states considered, the DA condition exhibits a consistently higher transformation rate than the SA condition, accompanied by a higher work-hardening rate. These findings highlight the coupled role of stress state and microstructural morphology in governing localisation behaviour and strain-induced transformation in medium-manganese steels. Full article

Aeolian sand is abundant in arid deserts, but its high replacement in cement-stabilized bases can reduce strength and raise cracking risk. Strain localization and crack evolution are also poorly quantified. This study aimed to optimize the early age performance of cement-fly ash stabilized aeolian sand gravel (CFSAG) and clarify its failure mechanism. A Box–Behnken response surface methodology varied the cement content, cement-to-fly ash ratio, coarse aggregate gradation, and aeolian sand content. The 7-d unconfined compressive strength (UCS) and splitting tensile strength (STS) were tested. Digital image correlation (DIC) recorded full-field strains and crack metrics in compression and splitting. SEM–EDS was used to interpret microstructural changes. The aeolian sand content dominated UCS, whereas the cement content and cement-to-fly ash ratio mainly controlled STS. Factor interactions were non-negligible and supported the joint optimization of the two strength indices. DIC identified a crack propagation threshold near 0.9 P_max in splitting. Excess aeolian sand (>50%) caused earlier localization, more cracks, and wider openings. In the appropriate amount of aeolian sand mixtures, hydration products filled voids and improved paste continuity. SEM–EDS indicated that excessive fines increased porosity and weakened the interfacial transition zone. Overall, the combined RSM–DIC–SEM approach links mix design with deformation and microstructure evidence. It provides practical guidance to balance strength and cracking resistance at early ages for cement-stabilized bases in desert highway engineering. Full article

The Felbertal tungsten mineralisation in the Tauern Window (Eastern Alps) is hosted by the Early Paleozoic Habach Complex belonging to the Lower Schieferhülle. In predominantly mafic meta-volcanic rocks, mostly amphibolites, green amphibole crystallised in assemblages with plagioclase, epidote, chlorite, sphene and quartz. Microstructural features and preferential orientation of the amphiboles define planar-linear structures of finite strain and indicate that their crystallisation is coeval to the main deformation event. Amphibole crystals display core-to-rim zonations with increasing ^IVAl, ^VIAl, Na and Ti and decreasing Si, covering actinolite over magnesio-hornblende to tschermakite compositions. Amphibole zonations and assemblages are similar to metabasites in the classical Barrovian mineral zones in the Dalradian of Scotland and typical of a prograde metamorphism from the greenschist over epidote-amphibolite to the lower amphibolite facies. Amphibole endmember geothermobarometry defines an early P-T path segment from 400 °C/2 kbar to 540 °C/6 kbar, and a consecutive later P-T path segment from ~500–540 °C/6 kbar to maximal P-T conditions of ~620–640 °C/7–8 kbar. As Carboniferous granitoid intrusions within the Habach Complex underwent penetrative ductile deformation, an Alpine Tertiary age of the lower amphibolite facies metamorphism, as observed in other parts of the Lower Schieferhülle, appears suitable. Full article

Edge cracking severely limits the rolling yield of magnesium alloy plates. A novel lattice severe deformation rolling (LSDR) process using corrugated rolls is proposed to suppress edge cracking. Numerical simulations, rolling experiments, and microstructural analyses were conducted, with results compared to conventional flat rolling (FR), to elucidate the suppression mechanism. LSDR induces a multi-peak stress distribution and restricts metal flow, thereby reducing additional stresses responsible for edge cracking. Deformation heat generated in local severe deformation zones compensates for thermal loss, alleviates the temperature gradient between the plate edge and center, and enhances overall plasticity. According to the Cockcroft–Latham fracture criterion, LSDR effectively limits damage growth and confines damage within a single lattice, suppressing crack propagation, whereas FR produces damage values far exceeding the critical value of 0.43. Furthermore, fine grains formed in severe deformation zones, together with dislocation entanglement induced by twinning, impede crack propagation. This work demonstrates the effectiveness of LSDR and provides a new approach for mitigating edge cracking in rolled metal plates. Full article

Traditional homogeneous copper foils suffer from a trade-off between strength and ductility, while gradient or heterogeneous structures are mostly based on deformation processing, making it difficult to achieve controllable construction within a thickness of ≤10 μm. This study aims to directly construct a layered structure with a “fine–coarse–fine” (A-B-A) gradient grain distribution, denoted as 3L-ABA in an 8 μm copper foil via direct current electrodeposition, which utilizes composite additives to regulate electrochemical polarization and nucleation modes. Through systematic characterization and mechanical testing, it was found that the 3L-ABA copper foil exhibits a tensile strength of 604 ± 18 MPa, an elongation of 3.6 ± 0.25%, and low surface roughness Rz of 0.46 μm. Microscopic mechanism analysis demonstrates that the gradient structure achieves synergistic strengthening and toughening through surface fine-grain strengthening, intermediate coarse-grain coordinated plastic deformation, combined with dislocation density and twin strengthening. Electrochemical tests confirm that Additive A (containing collagen, bis-(3-sulfopropyl)-disulfide (SPS), thiourea and 2-mercapto-5-benzimidazolesulfonic acid sodium salt (2M5S)) induces strong cathodic polarization, promoting instantaneous nucleation and grain refinement, whereas Additive B (containing collagen and bis-(3-sulfopropyl)-disulfide (SPS) shows weaker polarization and promotes grain growth. This research provides a scalable electrodeposition solution for the microstructural design and performance regulation of ultra-thin copper foils. Full article

In the aerospace field, the BT25y titanium alloy is recommended as a candidate material for manufacturing compressor discs and rotor blades of aircraft engines. The influence of hot deformation parameters on the microstructural evolution, recrystallization softening, and globularization mechanism of the BT25y alloy with an initial lamellar structure was studied. Furthermore, the coupling relationship between dynamic recrystallization and lamellar globularization was explored by means of EBSD, SEM, and TEM techniques. The experiment results indicate that the characteristics of initial lamellar α, α/α sub-grain boundaries within α lamellae, and the α/β phase boundary show significant variations due to the formation of equiaxed α grains during hot deformation. As the strain rate increases, the recrystallization mechanism of α phase gradually shifts from CDRX softening characterized by sub-grain evolution and lamellae fracture, to DDRX softening characterized by grain boundary arching and sub-grain boundary bridging. As the deformation temperature increases, the intense thermal activation promotes the accumulation of distortion storage energy, providing enhanced driving force for the occurrence of dynamic recrystallization. The research results will contribute to a deeper understanding of the relationship between dynamic recrystallization and lamellar globularization, providing theoretical guidance for the deformation process optimization and mechanical property control of the BT25y alloy. Full article

The microstructure and properties of a cobalt-free, cost-effective Al_0.4CrFe₂Ni₂ medium-entropy alloy (MEA) after multi-stage thermomechanical processing, including annealing, rolling over a wide temperature range from hot to cryogenic conditions, and subsequent precipitation strengthening, were investigated in the present study. The initially cast microstructure was effectively homogenized through hot rolling with an 80% thickness reduction followed by homogenization annealing, resulting in the formation of a single-phase supersaturated solid solution and enhanced stability of plastic deformation. Strengthening of the MEA was achieved by rolling under both ambient and cryogenic conditions, with the deformation process predominantly governed by shear band formation. However, rolling under cryogenic conditions led to a more pronounced localization of plastic deformation, promoting the formation of deformation nanotwins and resulting in significantly higher strengthening compared to ambient rolling, with the alloy reaching a yield strength of 1040 MPa and an ultimate tensile strength of 1235 MPa. Precipitation hardening was governed by the formation of B2-type (ordered body-centered cubic, BCC) precipitates, which preferentially nucleated along deformation bands, thereby effectively strengthening the alloy to a yield strength of 1420 MPa and an ultimate tensile strength of 1465 MPa. Our results demonstrate that the investigated MEA offers a wide range of tunable mechanical properties, which can be effectively tailored through appropriate combinations of thermomechanical processing routes. Full article

This study investigates the as-cast Mg-8Gd-1Y-2Sm-1.2Zn-0.5Mn (wt.%) alloy with high rare-earth content. Solution treatments were conducted at 480 °C, 520 °C, and 560 °C for 6–10 h. Microstructure and mechanical properties were characterized using OM, XRD, SEM-EDS, and compression testing. The as-cast alloy shows a dendritic structure with continuous grain-boundary phases (Mg₅RE, W, and LPSO), exhibiting a compressive yield strength of 145 MPa, ultimate strength of 238 MPa, and fracture strain of 12.66%. Solution temperature has a critical influence on phase dissolution and grain refinement. Notably, the overall plasticity of the material did not show a significant dependence on the specific solution temperature or holding time within the studied range. Treatment at 520 °C produces the most balanced microstructure: clear grain boundaries, extensive phase dissolution, refined grains, and enhanced solid-solution strengthening. Specifically, 520 °C for 10 h results in the finest and most uniformly distributed residual phases, a homogeneous matrix, the highest compressive strength, and suitable conditions for subsequent aging, thus being identified as optimal. Fractography reveals a transition from quasi-cleavage in the as-cast state toward enhanced ductility after solution treatment. However, small cleavage facets after 10 h are attributed to stress concentrations from rare-earth-rich regions and reduced deformation compatibility due to retained LPSO phases. Full article

Fe-Ni-based alloys have attracted attention due to their potential for applications such as transmission line de-icing, where the core requirements include a Curie temperature near the freezing point and sufficient saturation magnetization. Accordingly, this study designed an Fe-29Ni-2Cr-1.5Mn (at.%) alloy with a Curie temperature around the freezing point, aiming to investigate the correlation between microstructural evolution and magnetic properties after cold rolling and annealing. The alloy was cold-rolled by 65% and subsequently annealed at 873 K for 0 to 60 min. The study reveals systematic evolutions in the alloy’s microstructure and magnetic properties. During the initial annealing stage, recovery substructures predominantly formed within the deformed grains, accompanied by a reduction in dislocation density and lattice constant. In the later annealing stage, the recrystallized fraction increased, although complete recrystallization was not achieved. Texture analysis indicates that the intensity of the Cube texture strengthened from 0.48 to 1.13. Correspondingly, the saturation magnetization and Curie temperature increased by approximately 9.76% and 10.25%, respectively, in the early annealing period, and then stabilized thereafter. The early-stage improvement in properties is likely related to stress relief and lattice distortion relaxation during the recovery stage. The calculated magnetocrystalline anisotropy constant of this alloy at 273 K is K₁ = 126 ± 18 J/m³, indicating that the <100> direction is its easy magnetization axis. This study provides insights into optimizing the magnetic properties of this alloy through controlled annealing. Full article

This study examined the effects of laser shock peening (LSP) and LSP without protective coating (LSPwC) on the microstructure and corrosion behavior of 304L stainless steel using cyclic polarization testing. LSP enhanced corrosion resistance under mild sensitization (650 °C; 5 h) by inducing compressive stress and increasing dislocation density, stabilizing the passive film. Limited improvement was observed under severe sensitization (650 °C; 24 h). Deformation-induced martensite detected by XRD was attributed to mechanical polishing, not LSP. In contrast, LSPwC reduced corrosion resistance across all conditions due to Fe-rich surface oxides that impaired passivation. Full article

This study investigates the microstructural evolution and wear behaviour of aluminium 7075-based metal matrix composites (MMCs) reinforced with high-entropy alloy (HEA) particles and fabricated via friction stir processing (FSP). A detailed characterisation of the grain refinement in the 7075 matrix was conducted, revealing significant dynamic recrystallization and grain size reduction induced by the severe plastic deformation inherent to FSP. The interaction between the matrix and HEA particles was analysed, showing strong interfacial bonding, which was further influenced by post-processing heat treatments. These microstructural modifications were correlated with the wear performance of the composites, demonstrating enhanced resistance due to the synergistic effect of precipitates and particle reinforcement. The findings highlight the potential of FSP as a viable route for tailoring surface properties in advanced MMCs for demanding tribological applications. Full article

To address the performance deficiencies in welded joints in 2507 duplex stainless-steel pipes under demanding service conditions such as deep-sea operation, this study investigates drawn 2507 duplex stainless-steel pipes. Vacuum-fusion welding coupled with ER2507 wire filling is employed to fabricate the joints. The joint microstructure and tensile behavior are systematically analyzed using microstructural characterization techniques (electron backscatter diffraction and transmission electron microscopy) and uniaxial tensile testing. The results indicate that the joint exhibits a graded microstructure along the welding direction: base metal-heat affected zone-weld metal. The austenite phase fraction in the fusion zone decreases to 27.6%. The joint achieves an ultimate tensile strength of 833.3 MPa and a total elongation of close to 23%, demonstrating an excellent combination of strength and ductility. During tensile deformation, the ferrite and austenite phases undergo coordinated deformation. Strain is distributed relatively uniformly at low strain levels but localized preferentially within the fusion zone at high strain levels. Fractographic analyses reveal a ductile fracture mode. This research provides theoretical support and technical reference for optimizing welding processes and assessing the service safety of 2507 duplex stainless-steel pipes in deep-sea pipeline-engineering applications. Full article