Search Results (947)

This study systematically investigates the hot deformation behavior and microstructure evolution of Ti-3Al-2.5V-0.5Ni alloy under compression at temperatures ranging from 800 °C to 1010 °C and strain rates ranging from 0.1 s⁻¹ to 10 s⁻¹, with a maximum deformation of 75% (with a corresponding true strain of 1.4). An Arrhenius-type constitutive equation was developed, and a hot processing map was established using a dynamic material model (DMM). Microstructural evolution was characterized using electron backscatter diffraction (EBSD). A hot processing map delineated stable and unstable regions. Regions with high power dissipation efficiency (η) were identified at deformation temperatures of 850–880 °C with strain rates of 0.1–10 s⁻¹, and at 940–960 °C with strain rates of 1.5–10 s⁻¹. These regions show high recrystallization fraction and good processing performance. The instability zone was observed at about 900 °C and high strain rate, which should be avoided during processing. The microstructure analysis of different power dissipation efficiency regions was carried out in detail. The results show that the power dissipation efficiency is about 0.38 at the deformation temperature of 950 °C and the strain rate of 0.1 s⁻¹, accompanied by high dynamic recrystallization. However, when the deformation condition is 800 °C and 10 s⁻¹, the power dissipation efficiency is lower than 0.18, the degree of recrystallization is limited, and a large number of dislocations accumulate. In summary, the large strain rolling of Ti-3Al-2.5V-0.5Ni alloy should be processed in the high-temperature α + β phase region (850–900 °C) and low-to-medium strain rate range of 0.1–5 s⁻¹. The process conditions can promote high recrystallization fraction, good processability, and weakened crystallographic texture, thereby minimizing the anisotropy of the final sheet. This study provides theoretical guidance for the optimization of industrial hot processing parameters of the alloy. Full article

Friction stir welding (FSW) of dissimilar aluminium alloys often results in non-uniform microstructure and hardness distributions due to asymmetric temperature fields and material flow. The objective of this study is to establish a quantitative relationship between thermal history, microstructural evolution, and hardness distribution in dissimilar AA5052-H32/AA6061-T6 FSW joints by combining experimental characterisation with validated thermal modelling. AA5052-H32 and AA6061-T6 plates were welded under five different parameter sets. A thermal finite element model was developed in COMSOL Multiphysics to simulate temperature evolution during welding and was validated using embedded thermocouple measurements, with predicted peak temperatures ranging from 455 °C to 641 °C. Optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) were employed to characterise grain structure and dynamic recrystallisation (DRX) behaviour, while Vickers microhardness mapping was used to evaluate the local mechanical response. The results show that DRX occurred in the nugget zone (NZ), leading to significant grain refinement, with a minimum grain diameter of 6.07 µm, representing an approximately eightfold reduction compared with the base material AA5052-H32. In contrast, the thermo-mechanically affected zone (TMAZ) experienced limited recrystallisation due to insufficient plastic deformation and temperature. The lowest hardness was observed in the TMAZ on the AA5052-H32 side, with the hardness reduction of 22% primarily caused by work hardening loss. Hardness was also reduced by 34% on the AA6061-T6 side due to decreased precipitation strengthening caused by high temperatures. This combined experimental–numerical study provides a systematic thermal–microstructure–hardness framework for understanding and predicting local property variations in dissimilar FSW joints. Full article

Aluminum alloy composites are widely used in various high-end fields due to their ability to give full play to the advantages of each layer. However, the traditional three-layer aluminum alloy composite sheet cannot meet the current demand. In this study, composite rolling technology is adopted to combine three different alloys (4045, 3003, and 6061) for fabricating a 2.0 mm thick four-layer aluminum alloy composite sheet (4045/3003/6061/3003). The microstructure and properties of the composite sheet were analyzed by simulating the vacuum brazing process (595 °C/10 min) and artificial aging treatment (175 °C for 12 h), combined with characterization techniques including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the four-layer composite sheet exhibits lower Si diffusion after brazing, where the intermediate 3003 aluminum alloy layers effectively prevent the combination of magnesium (Mg) and the 4045 alloy. Compared with the brazed three-layer composite sheet the ultimate tensile strength and yield strength of the four-layer composite sheet after aging are increased by 139.7% and 326.6%, respectively, indicating significant improvement in its mechanical properties. This study provides a reference for the production of four-layer aluminum alloy composite sheet and contributes to the development of rail transit. Full article

To study the influence of freckle defects on the hot deformation behavior and the inheritance of dynamic recrystallization (DRX) structure in GH4706 alloy, the microstructures of specimens with and without freckles and the evolution laws of hot-processing parameters were compared. Hot compression experiments were conducted on a thermal simulation testing machine at 950–1150 °C, strain rates of 0.001–1 s⁻¹, and 55% deformation. Freckle-containing specimens were tested under DRX critical conditions. The flow stresses of both specimens increase with strain rate or with decreasing temperature. The power dissipation coefficient (η) and instability value (ξ) follow complex laws. Electron back-scattering diffraction (EBSD) was used to analyze DRX microstructures and nucleation mechanisms. The DRX degree of freckle-containing specimens is lower, with a larger average grain size. The DRX mechanism initiates preferentially in freckle-containing specimens, and its volume fraction changes in a complex manner. Grain coarsening occurs in freckle-containing specimens at high temperatures and low strain rates. Freckle defects lead to significant differences in the DRX mechanism of GH4706 alloy. Freckle-containing specimens exhibit both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), whereas freckle-free specimens primarily display DDRX and second-phase particle-stimulated nucleation (PSN). The presence of MC carbides and Laves phases within freckle defects provides nucleation sites, further supporting a typical second-phase particle-stimulated nucleation mechanism. Full article

This study systematically investigated the static recrystallization behavior and microstructural evolution of cold-rolled Ti-2Al-2.5Zr alloy tubes subjected to isothermal annealing at 650–800 °C. Electron backscatter diffraction (EBSD), optical microscopy, and microhardness testing were used to analyze recrystallization kinetics, grain size, grain boundary character, texture evolution, and strain energy release under different annealing temperatures and times. The results show that with increasing annealing temperature, the recrystallization incubation time is significantly shortened and the recrystallization rate increases nonlinearly; the times required for full recrystallization at 650, 700, 750, and 800 °C are 480 min, 25 min, 20 min, and 15 min, respectively. Compared with the other annealing temperatures, annealing at 700 °C yields finer, more uniform equiaxed grains and lower texture intensity, while at higher temperatures, recrystallization and recovery proceed too rapidly, which is unfavorable for fine control of the microstructure. After completion of recrystallization, the alloy microhardness stabilizes at approximately 200 HV. Based on the Avrami kinetics model, the recrystallization activation energy of the Ti-2Al-2.5Zr alloy tubes was calculated to be approximately 303.9 kJ/mol, providing a theoretical basis for optimizing the annealing process. Full article

Eutectic alloys stand out for their ability to combine high strength and good ductility; a behaviour rooted in their characteristic two-phase microstructure—lamellar or globular—formed at a constant solidification temperature that minimizes segregation and suppresses brittle phases. Their low interfacial energy limits microcrack propagation, while interfacial sliding and dislocation blocking at phase boundaries enhance both strength and toughness. In this work, we investigate how controlled microstructural modifications influence the behaviour of the eutectic high-entropy alloy AlCoCrFeNi2.1, composed of B2 (Ni–Al-rich) and L12 (Co–Fe–Ni-rich) phases. Because these phases exhibit distinct mechanical responses, microconstituent morphology becomes a design parameter. Powder metallurgy is the only processing route capable of providing the level of microstructural control required in this study. It preserves the rapidly solidified eutectic architecture of gas-atomised powders while allowing its intentional transformation during consolidation. Two strategies were implemented: (i) tuning the thermal–electrical input in Spark Plasma Sintering (SPS) and Electrical Resistance Sintering (ERS), and (ii) engineering the particle size distribution, including a bimodal design that enhances surface-energy-driven morphological transitions. SPS enables a gradual lamellar-to-globular evolution, whereas ERS induces ultrafast transformations governed by current intensity. The bimodal PSD significantly accelerates globularisation at lower energy input. EBSD-KAM (Electron Backscatter Diffraction—Kernel Average Misorientation) mapping identifies the lamellar B2 phase as metastable and highly strained, while globular B2 domains show reduced dislocation density. Nanoindentation confirms that intrinsic phase properties remain unchanged, whereas microhardness scales with morphology and lamellar spacing. These results demonstrate that the macroscopic mechanical response is governed by microstructure, establishing powder metallurgy as a uniquely powerful pathway for microstructure-driven design in eutectic HEAs. Full article

Hybrid nanocomposites based on Aluminum 6061 (Al 6061) reinforced with carbon nanotubes (CNTs) and aluminum oxide (Al₂O₃) emerge as promising materials due to their ability to achieve simultaneous improvements in strength, thermal stability, and tribological performance. This study examines the structure–property relationships of CNT–Al₂O₃ nano-reinforced hybrid Al 6061, with particular emphasis on microstructural evolution and mechanical properties. The nanocomposites are fabricated via a powder metallurgy route, which enables optimized dispersion and homogeneous distribution of CNTs and Al₂O₃ within the aluminum matrix. Microstructural characteristics, interfacial bonding, and grain refinement are systematically analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Mechanical characterization demonstrates a marked enhancement in mechanical properties compared to Al 6061. The observed property improvements are attributed to synergistic strengthening mechanisms, including effective load transfer from the matrix to Al₂O₃ particles, CNT-induced grain refinement, and increased resistance to dislocation motion. These results establish a direct correlation between microstructural features and mechanical performance, highlighting the potential of CNT–Al₂O₃ reinforced Al 6061 hybrid nanocomposites for lightweight, high-strength applications in aerospace, automotive, and structural engineering industries. Full article

High residual stresses significantly impact component performance during laser powder bed fusion (L-PBF) of GH3536 alloy. This study systematically investigates the effects of five scanning strategies (X-Scan, XY-Scan, R67, CB90, CB67) on residual stresses and deformation behavior in laser powder bed fusion-formed GH3536 high-temperature alloy. This is achieved by establishing a thermomechanically coupled mesoscale finite element model and combining it with experimental validation. The model was developed on the ANSYS APDL platform using a sequential coupling algorithm. It comprehensively considered melting latent heat, material nonlinearity, and dead-body element technology. While ensuring computational accuracy, significant computational efficiency gains were achieved through geometric scaling and reasonable simplifications (e.g., neglecting evaporation effects and assuming material isotropy). Results indicate that the 67° interlayer rotational scanning (R67) significantly reduces residual stresses, attributed to the breaking of thermal accumulation symmetry by asymmetric scanning. Component deformation is primarily governed by thermal stresses, with simulation results showing less than 10% deviation from experimental measurements. Despite the model’s medium-to-small scale and omission of size effects, its predicted trends highly correlate with X-ray diffraction measurements, validating its reliability for scan strategy optimization. Electron backscatter diffraction (EBSD) analysis further examined grain size and orientation differences at the microstructural level under the R67 strategy, revealing a more refined grain structure and KAM values. This provides theoretical support for L-PBF forming of nickel-based high-temperature alloys. Full article

Existing macroscopic finite element models for electron beam welding (EBW) typically assume isotropic material behavior, often failing to accurately predict residual stresses induced by strong crystallographic textures. To address this limitation, this study established a sequential dual-scale coupled numerical model bridging micro-texture to macro-mechanics by combining the crystal plasticity finite element method (CPFEM) with thermal-elastic-plastic theory. Representative volume elements (RVEs) incorporating α and β dual-phase characteristics were constructed based on electron backscatter diffraction (EBSD) data from the TA15 weld cross-section. Through simulated tensile and shear calculations on the RVEs, homogenized orthotropic stiffness matrices and Hill yield constitutive parameters were derived and mapped onto the macroscopic model. Simulation results indicate that the proposed model maintains the prediction error for molten pool morphology within 16.3%, while effectively correcting the stress overestimation inherent in isotropic models. Specifically, it adjusts the peak longitudinal residual stress at the weld center from 800 MPa to approximately 350 MPa, significantly reducing the anomalous “M-shaped” stress distribution. By successfully capturing shear stress components, this work provides a high-fidelity computational approach for predicting complex stress states in welded joints, offering critical insights for structural integrity assessment. Full article

Magnesium alloys’ poor corrosion resistance limits their applications as biodegradable bone repair materials. Alloying tailors Mg alloys’ microstructure and properties. The present study investigates the effect of 2 wt.% Ag addition on the microstructure and initial corrosion behavior of hot-rolled Mg-1Ca alloy. Mg-1Ca and Mg-1Ca-2Ag alloys were prepared by melting using Mg-2Ca and Mg-4Ag master alloys, followed by homogenization at 400 °C for 2 h, hot rolling, and stress-relief annealing at 400 °C for 6 h. The alloys were systematically characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Initial corrosion behavior was evaluated via 3 h immersion tests in simulated body fluid (SBF). Results reveal Ag’s high thermal diffusivity promotes segregation at tensile twin boundaries, forming Ag₃Mg nanoparticles. These nanoparticles hinder grain boundary migration and, with increased deformation, facilitate grain rotation and high-angle grain boundary formation, weakening texture. Internal stress accumulation near twin boundaries—driven by grain orientation variation and nanoparticles—induces ~86° rotation of {10–12} tensile twins around the c-axis, forming double twins. During corrosion, nanoparticles and double twins synergistically promote dense protective film formation, significantly reducing corrosion rates. Full article

The AA7075 holds significant importance in the aerospace field. Understanding its microstructure evolution and constitutive relationships during warm deformation is crucial for optimizing forming processes. To this end, isothermal compression experiments were conducted at different temperatures and strain rates to analyze their flow stress behavior. The microstructure evolution was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Microstructural analysis confirmed that dynamic recovery constitutes the predominant softening mechanism under warm forming conditions. The results indicate that flow stress is highly sensitive to deformation parameters, decreasing with increasing temperature and rising with increasing strain rate. To accurately describe the flow behavior, two distinct constitutive models were formulated: (1) a phenomenological Hensel–Spittel–Garofalo (HSG) model; (2) a novel hybrid machine-learning model that innovatively integrates the Harris Hawks Optimization (HHO) algorithm with an LSTM model. Both constitutive models demonstrate reasonable predictive accuracy. In comparison, the HHO-LSTM model demonstrated a superior ability to capture complex nonlinear relationships, achieving highly precise predictions of flow stress across the full range of deformation conditions tested in this work. The hybrid machine-learning model proposed in this study provides a highly accurate method for describing and predicting the flow behavior of the AA7075 during warm forming, offering a powerful predictive tool for engineering applications. Full article

With the ongoing miniaturization of solder joints in three-dimensional integrated electronic packaging, electromigration reliability has become a pressing concern. This study systematically examines the interfacial intermetallic compound (IMC) growth behavior of Cu/Sn-58Bi/Cu joint under electromigration (EM) with a symmetrical square-wave alternating current (AC). Electron backscatter diffraction (EBSD) was employed to perform statistical spatial analysis of Sn grain orientations within the joints to reveal the growth mechanism of interfacial IMC. Results demonstrate that the AC field markedly enhances the anisotropy of IMC growth in Cu/Sn-58Bi/Cu joints, exhibiting two phenomena: uniform growth on both sides and rapid growth (polar growth) on one side of the interfacial IMC. Among them, the IMC thickness difference characterization quantity Δ_IMC reached as high as 45.56% for the latter. This is attributed to the directional regulation of atomic migration rate by Sn grain orientation (the angle θ between the c-axis and the electron flow) and is further amplified by the altered atomic diffusion pathways imposed by the Bi phase distribution. Specifically, the Sn grains exhibit a pronounced preferential orientation mode along the current path (horizontal direction), with an orientation gradient of 0.915 μm⁻¹. The arrangement of Bi-rich phases alters the distribution of Sn grains in Cu/Sn-58Bi/Cu joints, thereby reshaping the internal electron transport pathways and significantly intensifying the orientation-dependent effect of IMC growth. Moreover, Sn grains adjacent to the Bi-rich phase boundaries (phase boundary grains) display a stronger tendency for c-axis orientation parallel to the current direction, exhibiting an average effective orientation parameter 1.948 times greater than that of bulk grains, which establishes a well-defined spatial orientation gradient. Full article

The microstructural and textural evolution in hot-rolled Fe–3.0 wt.% Si steel sheets was investigated by quasi in situ electron backscatter diffraction (EBSD) analysis. During recrystallization, the Goss texture intensity in the surface region remains essentially unchanged, whereas the α and α* textures are strengthened. In the center region, the α texture weakens, and the α* texture shows little variation, while the Goss texture becomes intensified. In the surface region, {112}<110> recrystallized grains nucleate by consuming deformed matrices with orientations near {114}<221> and {110}<112>. Recrystallized {114}<481> and {001}<210> grains consume deformed matrices near {114}<221> and Goss orientations, while Goss grains nucleate by consuming Goss-oriented deformed matrices. In the center region, {112}<110>, {114}<481>, and {001}<210> recrystallized grains nucleate and grow by consuming α and λ type deformed matrices, whereas Goss recrystallized grains preferentially consume deformed matrices with orientations of {111}<112>. 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

Inverse pole figure mapping is a common orientation visualization method used in electron backscatter diffraction (EBSD) software to display crystal orientations. Although this technique has been routinely used in commercial EBSD software, the coloring algorithm employed to map the orientation and construct the color key (standard stereographic triangle) has not been reported in the literature. This paper presents a simple algorithm to color the standard stereographic triangles of the 11 Laue groups by mapping the Maxwell color triangle to the curved standard stereographic triangles using nonlinear shape functions commonly employed in finite element methods. Detailed procedures are given to illustrate how the mapping is performed and how it is used to construct inverse pole figure maps from Euler angles. Color coding of the seven different standard stereographic triangles is demonstrated using a computer program written in C++. It is shown that the simple color-coding algorithm presented in this paper can be conveniently utilized to display orientation data in inverse pole figure maps, which is a critical part of designing customized EBSD software. It also provides a method to adjust the color center within the curved triangles to more uniformly distribute the color, which is not available in commercial EBSD software. The algorithm can also be used to design orientation representation software for other applications, e.g., crystal plasticity simulations, where representation of orientation data is also a routine task. Full article