A novel Be-Al-Ag-Co-Ge (BA-A) alloy was prepared to address the limited understanding of strain rate sensitivity and fracture mechanisms in multi-element modified Be-Al systems, and investigated tensile properties within strain rate range of 0.001 to 0.05 s-1. BA-A alloy exhibits typical dual-phase microstructure consisting of equiaxed Be particles embedded in continuous Al matrix. Experimental results demonstrate a significant strain-rate strengthening effect: ultimate tensile strength (UTS) increases from 217.0 MPa to 237.4 MPa with increasing strain rate, while elongation decreases from 1.52% to 1.28%. Strain rate sensitivity factor shows non-monotonic trend, initially decreasing and then increasing. Although cleavage fracture of Be phase dominates across the entire strain rate range, the Al phase exhibits more pronounced ductile features at lower strain rates. As the strain rate increases, the cleavage fracture becomes increasingly dominant. This synchronized variation in macroscopic mechanical behavior and fracture characteristics originates from the inherent deformation incompatibility between the soft Al phase and hard Be phase. This incompatibility evolves with strain rate and governs the macroscopic response by regulating the density and distribution of dislocations at Be/Al interface. The study clarifies the role of deformation incompatibility as a critical bridge connecting microscopic mechanisms with macroscopic rate-sensitive performance, providing theoretical guidance for design of dynamic-loading-resistant Be-Al-based alloys.

The morphology of primary alpha-Be dendrites during the solidification process directly determines the porosity defect and thus the mechanical properties of beryllium-aluminum alloys. However, the features of the threedimensional microstructure remain unclear, and how the structure evolves under the complex multiple physical fields still requires to be explored. Here, X-ray microtomography characterisations were conducted to uncover the three-dimensional dendritic structure of the hexagonal close-packed (HCP) alpha-Be dendrite with 12 preference growth directions. A thermal-fluid-solute-microstructure fully-coupled model was developed to describe dendritic morphology evolutions under the solute transport driven by the natural convection. The results reveal that the Al element significantly enriched at the solid-liquid interface drove an intense downward natural convection, accelerating outward solute transport from the roots of the dendritic branches. Furthermore, due to the in-phase arrangement of growth directions on both sides of {0001}, the unique symmetrical structure of alpha-Be dendrites induces solute distribution and thus the asymmetric melt flow. Such asymmetry inhibits the secondary dendrite arm growth in some directions, ultimately resulting in the hard-to-identify asymmetric threedimensional dendritic structure. Accelerated solute transport also leads to the increase in the secondary dendrite arm spacing and the decrease in the interfacial area density. As the temperature approaching to 1431 K (the temperature at which the liquidus slope approaches to zero), a rapid increase in solid fraction occurs and thereby induces frequent grain coalescences, causing an additional increase in the melt flow velocity by compressing the space and enhancing the solute enrichment.

Functionally graded materials (FGMs) are widely used in high-end fields like aerospace and energy for their customizable gradient properties, yet accurate detection of subtle defects in their inhomogeneous structures remains a key challenge for conventional non-destructive testing (NDT) techniques. To address this, this study proposes a multi-task learning-based phased array ultrasonic testing (PAUT) system for FGM defect inspection, featuring a multi-task neural network integrating CNN, RNN, and ensemble learning, plus gradient-corrected acoustic modeling, multi-scale feature extraction, and 3D reconstruction. A physic dataset was built based on Ti6Al4V-ZrO2 FGM acoustic properties, incorporating gradient-induced wave distortion and Gaussian/speckle synthetic noise. The system’s CNN extracts B-scan spatial features and LSTM captures A-scan temporal dependencies, enabling synergistic defect localization and quantification via a combined loss function optimized by Pareto multi-objective strategy. Experimental results show high detection accuracy for different size defects. Transfer learning adapts it to Al2O3-Ni FGMs and trained/validated on 5 defect types with Bayesian uncertainty quantification ensuring reliability. This work provides a physics-informed solution for FGM inspection, overcoming single-modal NDT and homogeneous-material model limitations, and supports intelligent testing system generalization in FGM-based high-end manufacturing.

To explore the influential mechanism of electrode polarity in self-shielded flux-cored arc welding (SS-FCAW) on arc behavior, aiming at the problem that the complex metallurgical reactions make it difficult to construct a numerical model that conforms to the actual situation. Based on the numerical simulation method of computational fluid dynamics (CFD) and the theory of magnetohydrodynamics, a two-dimensional numerical model of arc plasma was constructed. The distribution characteristics of the arc plasma temperature field, current density field, and flow field under different electrode polarities are studied. The results show that the temperature distribution characteristics of the simulated arc are consistent with the experimental spectral analysis results, thereby verifying the effectiveness of the model. Under direct current electrode negative (DCEN), the conductive channels at the bottom of the droplet are radially divergent, resulting in a "gas ball" temperature distribution; under direct current electrode positive (DCEP), the conductive area was relatively small, so the temperature distribution is "long strip". In addition, compared with DCEN, the temperature, current density, and flow velocity of arc under DCEP increase by approximately 26 %, 235 %, and 445 % respectively at 120A; the current increased from 80A to 120A, highest temperatures of arc under DCEN and DCEP increase by approximately 4.5 % and 2.5 % respectively, the current densities increased by 24.8 % and 39.8 %, and the flow velocities increased by 51.7 % and 83.3 %.

Magnesium (Mg) alloys is constrained by its low boiling point and poor plastic processing properties, resulting in high production costs of additive manufacturing components as the primary challenges. The heterostructure multiscale rare earth precipitates are discovered from WE43 deposited component fabricated by strip laser-directed energy deposition (SL-DED) additive manufacturing technology. Specifically, these formed precipitates consist of nano-scale HCP Mg2Y phases dispersed within network like micro-scale β'' face-centered cubic (FCC)/body-centered cubic (BCC) Mg24Y5 phases throughout the boundaries of equiaxed α-Mg grains. This microstructure enables the fabricated WE43 alloys with average ultimate tensile strength of 235.1 MPa and 9.7% elongation, surpassing most existing WAAM-produced WE43 alloys. The synergistic interaction of multi-scale precipitates facilitates the accommodation of dislocations and stacking faults, activating slip systems with high critical resolved shear stress to accommodate twinning and no-basal slip, and thereby conferring exceptional deformability. This work effectively provides a low-cost additive manufacturing strategy and deepens the understanding of the plastic deformation of rare earth Mg alloys.

This study reports a novel strategy for strengthening and toughening aluminum-matrix interfaces using nanosized oxide core–shell heterostructures. By leveraging optimized oxidation and tailored ball milling of high-entropy alloy (HEA) reinforcements, nanoscale oxide core–shell heterostructures were constructed in aluminum matrix composites, yielding exceptional strength–ductility synergy. Nano-MgO formed in situ within α-Al matrix and along α-Al grain boundaries under influence of plasma activation. Oxidized HEA (OHEA) reacted with Mg, leading to in situ formation of laminated Al2O3–Cr2O3–MgAl2O4. The gradient heterointerfaces induce a synergistic strengthening effect governed by two dominant mechanisms: Orowan strengthening derived from dislocation pinning by dispersed nano-MgO particles and heterostructure interfacial strengthening originating from the laminated oxide transition zone. The latter effectively mitigates interfacial stress concentration and facilitates efficient load transfer. Consequently, OHEA/Al composite exhibits significant mechanical improvements, with σuts, σy, and εf increased by 11.1

In this study, Be-Al and Be-Al-Ag-Co-Ge alloys were fabricated by investment casting, and the effects of Ag, Co and Ge elements on the microstructure and mechanical properties were investigated. The results demonstrated that the addition of Ag, Co and Ge reduced the secondary dendritic arm spacing of Be, leading to a morphological transition of the Be phase from columnar dendrites to spherical equiaxed grains. Concurrently, Ag and Co atoms diffused toward the Be/Al interface driven by interface energy minimization, forming segregations that enhanced the interface adhesion work and consequently improved the Be/Al interface bonding strength and mechanical properties of the Be-Al alloy. In addition, uniformly distributed Ag2Al nanoparticles were formed within the Al phase. Compared to the Be-Al alloy, the Be-Al-Ag-Co-Ge alloy exhibited enhanced mechanical properties, with yield strength of 228.2 MPa, ultimate tensile strength of 272.3 MPa, and Vickers hardness of 115.72 HV, representing increases of 106.07%, 85.87% and 97.67% respectively. The strengthening mechanism of the Be-Al-Ag-Co-Ge alloy was analyzed using a theoretical model, revealing that Ag2Al precipitates dominate the yield strength enhancement, contributing 50.78 MPa primarily through Orowan, GND, and CTE mismatch strengthening. This work provides an effective strategy for optimizing the microstructure and enhancing the mechanical properties of Be-Al alloys.

With the need for energy saving and emission reduction, the process of wire arc directed energy deposition (WADED) of large-scale, high-precision Mg alloy parts is becoming more widely recognized. However, the poor deformation ability remains a significant challenge that limits its wide application. In this work, the solidification rate and supercooling degree of Mg alloy during WADED process were increased by controlling the interlayer cooling time, and the dispersed micrometer and nanometer dual-scale Al8Mn5 phases were successfully precipitated. The formation mechanism of dual-scale Al8Mn5, microstructural evolution, and their effect on the deformation behavior were comprehensively investigated. The mechanical properties were essentially the same in the build direction and the travel direction, with an average ultimate tensile strength of 236.9 MPa and an elongation of 30.52%. The distribution of double-scale Al8Mn5 impedes the dislocation movement, stimulates the opening of non-basal slip systems, and promotes slip-twinning interactions during plastic deformation. This study offers insights into the design and enhancement of high-performance Mg alloy.

In order to overcome the contradiction between additive efficiency and higher laser power and wall thickness limit, and to obtain the desired heterostructured thin-walled components, an innovative laser penetration strip additive manufacturing (LPS AM) technology is presented. We apply the LPS AM technology to the direct fabrication of thin-walled 304 L steel with heterogeneous lamellar structures (HLS), which consisting of periodic equiaxed grain regions (EGR) and columnar grain regions (CGR). EGR presents a spherical austenite matrix with some nano-sized irregular ferrite grains, while CGR presents columnar austenite grains segmented by banded/ globular ferrites of different sizes to form a special nano-columnar biphase structure. Periodic HLS 304 L, with non-uniform grain sizes and different phases ranging from nanometers to micrometers, provides a synergistic strengthening effect and strain distribution capability, achieving high Heterogeneous Deformation Induced (HDI) strengthening and hardening. The TRIP effect, HDI strengthening and HDI strain hardening contribute to high strength and plasticity for HLS 304 L alloy. This innovative approach has the potential to be applied to the production of other thin-walled alloys with hierarchical structures and superior strength.

Construction of heterostructures represents a highly promising strategy for overcoming the strength-ductility trade-off in metal matrix composites. However, achieving well-controlled heterogeneous interface remains a significant challenge in the high-entropy alloy (HEA) reinforced matrix composites. In this study, a surfacemodified dual-phase HEA reinforcement (denoted as (A + O)HEA) was constructed through two-step heat treatment method: first introducing FCC phase by annealing single-phase HEA powders at 900 degrees C under argon atmosphere, followed by introducing surface oxygen doping via annealing at 700 degrees C in air. Then heterogeneous core-shell structures formed through in-situ interface reaction strategy during sintering process, thereby achieving simultaneous improvement in the strength and ductility of Al matrix composite. During spark plasma sintering (SPS), plasma-induced destabilization of the unstable oxygen-rich BCC and sigma phases triggered the fragmentation of FCC precipitates into nano-sized FCC particles, leading to the in-situ formation of a heterogeneous core-shell structure with the oxide layer. Within this oxide layer, nano-scale FCC precipitates and Mg solid solution, induced by oxygen, were formed. Within the oxide layer, in-situ nano-scale FCC precipitates and oxygen-induced solid solution of Mg were formed. The resulting (A + O)HEA/Al composites exhibits ultimate tensile strength, yield strength, and elongation of 321.6 MPa, 189.5 MPa, and 6.9 % respectively, representing improvements of 14.1 %, 16.8 %, and 13.1 % compared to the HEA/Al composites. The oxides and the sigma nanophase within the outer shell effectively modulate the stress gradient during plastic deformation, accommodating homogeneous stress distribution and inhibiting crack propagation effectively. The oxygen-induced heterogeneous interface design provides new pathway for enhancing the mechanical property of composites.

Gradient structured (GS) titanium alloys produced via additive manufacturing (AM) technologies have attracted considerable interest due to their remarkable capacity to undergo additional strain hardening, thereby achieving heightened ductility. This paper introduces a novel laser penetrating strip (LPS) AM technique tailored for fabricating symmetric gradient titanium alloy thin-walled components. During the LPS additive process, the Marangoni vortex and center-spraying solidification of the dumbbell-shaped molten pool can facilitate the diffusion of stabilizing Fe atoms of the beta-phase from the center to the surface layer, leading to the formation of large amounts of nano-beta-phase. The violent vortex in the up and down layer of the molten pool, in conjunction with the segregation of Fe, enables substantial compositional subcooling in the surface layer, which in turn facilitates the development of fine equiaxial grains. By fully exploiting the layered Marangoni vortex and the elemental segregation behavior of the LPS molten pool, a nano-beta-phase reinforced symmetric GS titanium alloy was fabricated, comprising a coarse-grained center region (CGCR) and a fine-grained surface region (FGSR). The mechanical incompatibility between the nano-beta-phase reinforced FGSR and CGSR results in the formation of macroscopic strain gradients, thereby enhancing both strength and plasticity. This innovative approach has the potential to be applied to the fabrication of other thin wall alloys exhibiting hierarchical structures and superior strength.

To reduce the cost of additive manufacturing and improve the strength and plasticity of AZ91D magnesium (Mg) alloy, an effective directed energy deposition (DED) technique was proposed using metal strip as raw material and high energy density laser as heat source. Laser penetration of strips for additive purposes, defined as laserstrip DED process. The deposited components showed that equiaxed alpha-Mg grains, discontinuous (3-Mg17Al12, and multiscale Al8Mn5 phases were generated. The values for yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) acquired from the build direction (BD) were 141.0 f 1.2 MPa, 251.0 f 0.9 MPa, and 14.0 f 0.3 %, respectively. In contrast, the measurements taken from the traveling direction (TD) resulted in 156.0 f 1.6 MPa, 257.0 f 1.1 MPa, and 14.0 f 0.5 %, respectively. The introduction of laser oscillations facilitated uniform heat distribution, promoting overall grain refinement. The multi-scale Al8Mn5 phase was in-situ formed during deposition, and Al-Mn nanophase provided heterogeneous nucleation sites for the refinement of the (3-Mg17Al12. The deformation process induces tensile twins, forming a composite phase with the (3-Mg17Al12 phase and transfer of dislocations, which relieves the stress concentration and improves the plasticity of the material. During deformation, the multi-scale Al8Mn5 phase hinders dislocations within the matrix and induces {10-12} tensile twin by stress concentration. This paper provides ideas for additive manufacturing technology with low cost, and high performance.

The strength-ductility trade-off has long challenged particle-reinforced metal matrix composites (MMCs). This paper presents an Al–Mg layered double oxide (LDO consisted of Al2O3(1 2‾10)//MgAl2O4(004)//MgO(002) at the Al2O3 side, and a MgO(200)//Mg(1 1‾02) the Mg matrix side) architectured Al2O3/AZ91D composite. The intermediate LDO bonds the inner hard Al2O3 reinforcement and the soft AZ91D matrix, which is beneficial to the trade-off between strength and plasticity of ceramic particle reinforced MMCs. An effective load-transfer enhancement and easy dislocation-bypass across the LDO with a set of coherent pairs (Al2O3–MgAl2O4, MgAl2O4–MgO, MgO–Mg, contributes to this synchronization improvement of strength and plasticity. This work sheds some light on fabricating Mg matrix composites with high strength and ductility.

Corrosion-resistant and biocompatible films were fabricated on AZ91D Mg alloy substrates by varying their roughness levels using metallographic preparation and subsequent hydrothermal procedures. The coated films comprised a mixed structure of Mg(OH)2 and Mg-Al layered double hydroxides (LDH) and exhibited excellent compactness. Coating film thickness increased with decreasing surface roughness. Corrosion resistance was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy. Metallographic pretreatment influenced the chemical activity of the Mg alloy surface and helped modulate the dissolution rate of the Mg17Al12 phase during the hydrothermal procedure. With decreasing roughness of the Mg substrate, the Al3+ concentration gradually increased, accelerating the in-situ formation of the Mg(OH)2/LDH composite coating and improving its crystallinity. A thick and dense Mg(OH)2/LDH coating was synthesized on the Mg substrate with the least roughness, substantially improving the corrosion resistance of the AZ91D alloy. The lowest corrosion current density ((5.73 ± 2.75) × 10−8 A·cm−2) was achieved, which was approximately three orders of magnitude less than that of bare AZ91D. Moreover, the coating demonstrated biocompatibility with no evident cytotoxicity, cellular damage, and hemolytic phenomena. This study provides an effective method for preparing coatings on Mg alloy surfaces with excellent corrosion resistance and biocompatibility.

A hybrid welding technology including laser penetration root welding and narrow gap laser filling welding is proposed to realize the layered welded joint for DSS2205/X65 bimetallic thick plate. This hybrid technology is an effective way to produce an overall bidirectional gradient layered weld distinguished by the microstructural and elemental distribution. Especially, the laser penetration thin bimetallic composite plate with an appropriate parameters combination of laser penetration direction, power and welding speed can effectively inhibit solute mixing and diffusion between the upper base and lower cladding layers, resulting in a layered root weld with a metallurgically and mechanically bonded interlayer. Finally, the formation of bidirectional gradient microstructure, and its residual stress and mechanical properties are extensively discussed.

In this study, active interpass cooling using various compressed CO2 gas strategies was applied to wire-arc additively manufactured Ti–6Al–4V alloy, and as-manufactured microstructure characteristics, including phase composition, grain growth and microhardness, were fully explored by using Electron Backscattered Diffraction and hardness tester. Results show that rapid interpass cooling brings obvious martensite phase transformation, primarily from lamellar α grains to acicular α grains, to the deposited component. The microstructure tends to be fine-grained, disordered and displays reduced texture strength and increased dislocation density through visible coloration. This feature also exhibits high hardness values that brings an improvement in mechanical strength to deposited metal. Moreover, it is found cooling time variation could obtain better grain refinement than altering cooling gas flow rate during deposit, which is probably related to effective heat dissipation. The research findings can provide significant insight into microstructural evolution mechanism in wire-arc directed energy deposition process, and benefits to properties control.

This work firstly oxidizes single-phase high entropy alloy (HEA) to form FCC and BCC dual-phase structure, and also introduces multi-component nano-oxides on surface to prepare oxidized HEA (OHEA) reinforcements, followed by preparation of OHEA/Al composites by spark plasma sintering. The introduction of O element accelerates interdiffusion between OHEA and Al matrix. FCC phase inside OHEA evolves into soft phase, and BCC matrix phase evolves into hard phase, forming heterogeneous interface in OHEA/Al composites. During tensile process, cracks preferentially initiated in hard phase due to severe stress concentration, and the soft phase effectively retarded crack propagation. Compared with 2024Al matrix, yield strength, tensile strength, and elongation of OHEA/Al composites increased by 35.31%, 57.34%, and 63.33%, respectively, realizing excellent combination of strength and toughness. Grain refinement, thermal mismatch, Orowan, and load transfer strengthenings synergistically improve the performance. The proposed method provides a promising avenue to optimize the properties of composites by pre-oxidizing HEA particles to construct heterogeneous interfacial structure.

The strength-ductility trade-off has long challenged particle-reinforced metal matrix composites (MMCs). This paper presents a multi-component layered double oxide (LDO) interfacial structured Mg matrix composite with high strength and plasticity by introduction of Ce. The LDO contains multi-component irregular nanoparticles (MgO, CeO2, Al3Ce and MgAl2O4) bonding the matrix and MgAlCe. Especially, Ce atoms participates in the formation of Al3Ce and are absorbed on the growing tip of beta-Mg17Al12, which further refine the matrix grand and beta-Mg17Al12 grain significantly by inhibiting grain boundary migration. During loading, the multi-component LDO can significantly improve load-transfer enhancement and contribute to dislocation-bypass across the LDO/matrix interface. This unique multi-component interfacial structure and fine grains of MgAlCe-LDO nanoparticle reinforced Mg matrix composite contributes to the high ductility and strength (UCS:407 MPa, YS:232 MPa) by increasing 50.2%, and 139.2% without sacrificing ductility (strain 20.6%).

The urgent demands for more excellent mechanical properties to meet higher steam temperatures for 9Cr steels have been the driving force behind the increasing research efforts on heat treatment. This paper presents a systematic study of the effect of the ultra-fine martensite (ultra-fine M) and retained austensite (RA) obtained by austempering process on mechanical properties are studied by experimental observations and phase-field simulation. The results demonstrate that austempering leads to the split and incompletion of martensitic transition, producing a mixed microstructure consisting of lathy martensite(lathy-M), ultrafine martensite(ultra-M), and retained austensite (RA). Due to the change of local chemical free energy and elastic strain energy caused by the redistribution of C element, two types (isothermal and athermal) of ultra-M form by spontaneous nucleation and interfacial migration during austempering with appropriate temperatures. Further tempering produces dispersed finer M23C6 precipitated at the interfaces of high-dislocated ultra-M than lathy-M. Meanwhile, RA decomposes into fine globular M23C6 and ferrite. Consequently, a larger amount of ultra-M and RA in quenched state results in smaller effective grain sizes and smaller carbides' average size, leading to the enhancement of precipitation strengthening, grain boundary strengthening, and impact toughness. This work establishes the potential for tailoring the strength and impact toughness of 9Cr1.5Mo1Co steel by optimizing the ultra-fine martensite and retained austensite using austempering process.

Defective graphene can effectively improve the interface between graphene and Al matrix. To further improve the interface bonding between graphene reinforcement and Al matrix, chemical etching was proposed to generate nanopore defects on surface of graphene oxide (GO), forming porous reduced graphene oxide (P-RGO) reinforcement. P-RGO/Al hierarchical composites were prepared by electrostatic adsorption, ball milling, and spark plasma sintering. "P-RGO rich zones" were formed via uniformly distributing P-RGO into Al matrix, and thus a hierarchical structure consisting of "P-RGO rich zones" and "P-RGO free zones" was constructed. The results show that ultimate tensile strength (UTS, 339.8 MPa), yield strength (YS, 296.1 MPa), and elongation (& epsilon;f, 9.1 %) of P-RGO/Al hierarchical composites were 23.1 %, 78.1 %, and 9.6 % higher than those of GO/Al composites. Nanopore defects increased specific surface area of P-RGO and provided nucleation sites for the interfacial reaction. Al2O3 formed in situ at the nanopores and Al12Mg17 precipitated at the interface together improved the interfacial bonding and enhanced the load transfer. The hierarchical configuration established by "P-RGO rich zones" and "P-RGO free zones" arranged alternately in space promotes crack deflection and increases crack propagation path. This work provides a promising way for the fabrication of high-performance composites.