Improving the wear resistance of lightweight aluminum alloys is important for extending the service reliability of components. Laser powder bed fusion (L-PBF) offers a promising route for fabricating wear-resistant Al alloys through microstructural architecture control. In this study, an Al–Ce–Si–Mg alloy was fabricated by L-PBF, exhibiting a continuous nanoscale Al11Ce3 network embedded in the α-Al matrix. The as-built Al–Ce–Si–Mg alloy exhibited a lower wear rate than commercial 6061, 7075, and as-cast Al–Ce–Si–Mg alloys under dry reciprocating sliding conditions. By comparing the as-built sample with a spheroidized counterpart containing isolated intermetallic particles, this study demonstrates that the continuous intermetallic network acting as a strengthening skeleton can enhance resistance to plastic deformation and regulate wear-induced microstructure evolution. The network structure changes the subsurface evolution pathway from dynamic recrystallization-dominated grain refinement to boundary-mediated nanolaminated substructure formation during sliding. Micropillar compression further confirmed that the nanolaminated structure in the as-built alloy exhibited much higher yield strength and strain-hardening capacity, thereby helping to stabilize the protective oxide nanocomposite layer and enhance wear resistance. These findings provide a microstructure design strategy for wear-resistant additively manufactured Al alloys.

The effects of RE elements during solidification of advanced structural alloy are systematically reviewed, covering seven interconnected aspects: melt purification, inclusion modification, melt structure alteration, element microsegregation, matrix nucleation and growth, primary precipitate formation, and solidification defect control. Meanwhile, this review innovatively puts forward a trifactorial mechanism involving RE atoms, RE atomic clusters, and RE second phases, which is rooted in the inherent properties of these three RE forms. In particular, the inherent properties of RE atomic clusters and their effects on solidification behaviors remain insufficiently understood and warrant deeper research. Notably, recognizing the nonmonotonicity of RE effects is critical, as it arises from the coupling and competition of multiple mechanisms. A systematic perspective on heredity and interactivity deepens understanding of RE effects and mechanisms. Finally, this review proposes six directions for future research: prioritize investigations into melt structure alteration and solidification defect control; determine the optimal range of RE additions; extend the trifactorial RE mechanism to other processes; exchange and draw on research experience across different RE alloy systems; explore the non-additive effect of multi-RE additions and relevant mechanisms; quantify the contradictory and primary-secondary relations among RE effects or mechanisms to advance intelligent RE alloying.

The alloys strengthened by nanoscale γ" phase (a coherent strengthening phase with an ordered D022 structure), renowned for their exceptional mechanical properties, experience an accelerated strength reduction above 650 °C, restricting their high-temperature applications. The conventional explanation attributes this strength reduction solely to insufficient stability of the metastable γ" phase, which also hinders the investigation of its deformation mechanisms above 650 °C. In this study, a high-stability γ" phase is introduced into a NiCoCr-based multi-component alloy system, effectively suppressing its destabilization during high-temperature deformation up to 850 °C. Therefore, this alloy exhibits markedly improved resistance to strength degradation above 750 °C, with only a 4% reduction observed from 750 °C to 850 °C. However, a significant strength reduction (30% reduction) is still observed in this alloy from 650 °C to 750 °C, suggesting that γ" destabilization is not the predominant factor for strength degradation within this intermediate-temperature range. It is observed that the strength reduction from 650 °C to 750 °C originates from a pronounced reduction in dislocation shearing resistance of γ" particles, while the minor strength loss between 750 °C and 850 °C benefits from preserved γ" stability. This work offers novel insights into the temperature-dependent strength reduction mechanism of γ" phase, establishing a theoretical foundation for developing γ"-strengthened alloys.

Solidification processing allows for the net shape manufacturing of complex superalloy components. However, unexpected plastic deformation during solidification is inevitable, and its accurate prediction remains challenging, largely stemming from constitutive models at extremely high temperatures (0.8 T-m similar to 1.0 T-m). Although well-established for service and deformation forming conditions, the deformation behaviors at such extremely high temperatures remain less explored. Here, we propose a high-accuracy (R-2 = 0.9998) unified constitutive model to characterize the mechanism transitions from creep to viscoplasticity over a wide range of temperatures from 0.8 Tm to 1.0 Tm in a gamma ' precipitate-strengthened nickel-based superalloy, based on high-temperature tensile experiments with strain rates in the range from 10(-5) s-1 to 10(-2) s-1 and strain rate jump tests in between. Above the gamma ' solvus, we find that five-power-law creep, controlled by dislocation climb, dominates and persists up to near the melting point. Below the gamma ' solvus, linearity of the stress exponent and apparent activation energy with respect to gamma ' volume fraction (R-2 > 0.9998) is identified, which suggests a transition to viscoplasticity controlled by gamma ' climb-bypass mechanisms. Notably, in contrast to the behavior traditionally observed in super-alloys, where variations in the apparent stress exponent are caused by a threshold stress, the absence of threshold stresses (confirmed with R2 > 0.9996) despite large variations in the stress exponent is revealed, which suggests no athermal energy barrier for bypassing the gamma ' phase at T > 950 C-degrees. The model developed is finally applied to simulate the distortion of a typical thin-walled investment casting with a displacement error less than 0.1 mm compared with industrial experiments, against a total distortion on the order of 3 mm. And for the first time, it quantifies the dominant role of creep in the distortion of Nickel-based superalloy casting components. This work offers a high-accuracy constitutive model to improve the creep-and viscoplasticity-induced distortion prediction accuracy of many high-temperature forming processes for nickel-based superalloys, such as investment casting, 3D printing, welding, and even hot isostatic pressing.

Liquid metal assisted cracking (LME) are a critical limitation in the performance of Zn-Al-Mg coated High Strength Steel (HSS) during resistance spot welding (RSW). To mitigate this issue, a flash nickel interlayer has been implemented on the steel surface. The mechanism by which the flash nickel interlayer mitigated LME is investigated, focusing on the combined effects of stabilizing grain boundaries and influencing crack plasticity. The findings demonstrate that the flash nickel interlayer induces grain refinement and optimizes grain orientation, enhancing dislocation accumulation near the crack tip to dissipate strain energy. This process increases the proportion of grains with Schmid factors between 0.4 and 0.5, dispersing local stress and altering the crack propagation path. The flash nickel interlayer reduces crack depth by 60.42% and crack quantity by 90.47%. Furthermore, it significantly enhances the strength and ductility of the welded joints, transitioning the fracture morphology from brittle-dominated to a brittle-ductile combination. Ni and Al additions strengthen Fe-Fe bonding and stabilize grain boundaries at the electronic level, whereas Mg addition weakens interfacial cohesion and thus promotes embrittlement. This study elucidates the mechanism of the flash nickel interlayer in mitigating LME across atomic, mesoscopic, and macroscopic scales, offering theoretical and experimental insights for the optimizing HSS during RSW processes and developing anti-embrittlement coatings.

Thin-walled components of advanced Ni-based superalloys pose significant challenges in manufacturing due to limitations in mold filling and microstructural control. This study elucidates the processing-microstructure-property relationships of a novel K439B superalloy fabricated via three distinct processes: Laser Powder Bed Fusion (LPBF) and Investment Casting including Gravity Casting (GC) and Counter Gravity Casting (CGC). The results reveal a stark trade-off between room-temperature (RT) ductility and high-temperature performance driven by intrinsic microstructural differences. CGC samples achieve a 10% increase in strength compared to GC samples, while LPBF samples increase 23% in yield strength and 179% in elongation, exhibiting superior RT strength-ductility synergy. This enhancement is attributed to the cellular structure strengthening and fine grain refinement. However, at high temperature, the LPBF specimens suffer from premature brittle fracture. Micro-structural evidence confirms that this degradation stems from the dissolution of dislocation cellular structures and rapid recrystallization, leading to dislocation annihilation and intergranular failure. In contrast, CGC specimens demonstrate the optimal balance of properties, particularly in creep rupture life, benefiting from reduced casting defects and coherent gamma ' precipitation strengthening. This work provides critical insights into the selection of processes for K439B, highlighting that while LPBF offers exceptional static strength, post-processing is indispensable for high-temperature service stability.

Conventional gravity casting (GC) inevitably causes pores, cracks, elemental segregation, and uneven phase distribution in Ni-based superalloys, which restricts the simultaneous improvement of strength and ductility. In this work, counter-gravity casting (CGC) is employed to prepare IN718 superalloys. The process–structure–performance relationship of the alloy is systematically analyzed via in-situ synchrotron X-ray diffraction and multiscale characterization. CGC, involving pressure-controlled filling and uniform thermal fields, markedly reduces defect clusters, refines and homogenizes γ″/γ′ precipitates, and suppresses grain-boundary δ-phase segregation. It also introduces residual compressive stress and improves the interfacial coherency. These microstructural changes lead to a fracture-mode transition from brittle intergranular fracture in heat-treated GC (HT-GC) alloys to ductile transgranular fracture in as-cast CGC (AC-CGC) alloys. Mechanical tests show that the AC-CGC alloy possesses an ultimate tensile strength of 1064 MPa and a fracture elongation of 16.1%, which are 13.9% and 22.0%, respectively, higher than those of the HT-GC samples. This study verifies that CGC can improve the microstructural uniformity and strength–ductility trade-off. The obtained results act as a valuable reference for developing high-performance metallic materials for the aerospace and energy industries.

Laser powder bed fusion (L-PBF) enables the additive manufacturing of nickel-based superalloys with complex geometries and high design flexibility, while avoiding conventional tooling. However, process instability-particularly spattering during laser-powder interactions-often induces internal defects that compromise mechanical performance. Here, we show that the uniform dispersion of HfO2 nanoparticles within the GH4169 superalloy simultaneously suppresses spattering, refines grains, and enhances mechanical properties. The nanoparticles were homogeneously coated onto the powder surfaces via ball milling and incorporated into the metallic matrix during L-PBF. Their presence markedly stabilized the melt pool by increasing both surface tension and viscosity, and promoted significant grain refinement and localized texture modification. Mechanical characterization revealed a 7.1 % increase in microhardness and a 9.5 % improvement in yield strength. These findings establish a nanoparticle-assisted strategy that couples process stabilization, microstructural optimization, and property enhancement, providing a mechanism-guided pathway toward application-oriented strengthening of metal matrix nanocomposites in additive manufacturing.

Thin-walled aluminum alloys,prized for their high specific strength,are critical to modern aerospace and other advanced industries.Counter-gravity casting(CGC)is a premier method for fabricating such components,where precise control over solidification microstructure is paramount.However,this control is challenged by the complex interplay of forced and natural convection during solidification.This study employs a coupled multiple-relaxation-time lattice Boltzmann(D2Q9)and quantitative phase-field model to simulate dendritic growth in a thin-walled Al-0.576wt.%Cu alloy.Simulations reveal that convection disrupts dendritic symmetry:for equiaxed crystals,solute plumes and asymmetric arm growth are observed,while for columnar dendrites,an optimal applied force exists that refines the microstructure without compromising economic viability.Furthermore,forced convection consistently reduces the inclination angle of primary dendrites.These findings,validated against experimental data,elucidate the micro-mechanisms of dendritic growth under convection,providing critical theoretical guidance for optimizing CGC processes.

The accuracy of the wax pattern used in the investment casting process directly affects the accuracy of the final casting. With the increasing complexity, integration and thinning of precision castings, the pressing and mold design of the wax pattern have encountered new challenges. Therefore, the numerical simulation of wax injection process is particularly necessary. The main goal of this study is to predict the dimensional deformation of the wax pattern and improve the surface quality of the wax pattern in the single ring multi support plates (the inlet section) by combining numerical simulation and experimental verification. Based on the property measurement of KC-2656 L wax material, the wax pattern forming process of three kinds of standard parts is numerically simulated by the Moldflow software, and the process parameters affecting the shrinkage and deformation of wax pattern are determined. This methodological innovation aims to improve computational efficiency and accuracy. Based on the single factor test results of the standard parts, the DOE test is designed, and the forming process of the wax pattern of the inlet section is numerically simulated. The mathematical model between the average volume shrinkage and the process parameters is established, and the best process parameters are obtained. The average volume shrinkage is reduced by 3.04

Cryogenic friction stir processing (CFSP) was applied to tailor the near-surface microstructure of a CoCrNi medium-entropy alloy and its tribological response. CFSP produced an ultrafine, twin-rich surface layer that significantly modified oxidation behavior and subsurface deformation during sliding. The CFSP sample formed a thin, dense, and stable Cr-rich amorphous tribo-oxide film, while the base material and air-processed alloy developed thick, cracked oxides prone to delamination. Beneath the CFSP tribo-layer, severe shear was accommodated through rapid grain subdivision, stacking-fault formation, and nano-twinning, effectively suppressing crack initiation. In contrast, the other samples experienced pronounced microcracking and abrasive wear. The results reveal that wear resistance in low-SFE alloys is controlled not by initial hardness but by tribo-oxide stability and the microstructural capacity to withstand friction-induced deformation. This work provides mechanistic guidance for microstructure-engineered wear optimization in medium-entropy alloys.

This study developed a novel non local dislocation-based crystal plasticity fast Fourier transform (CPFFT) model in DAMASK to quantify the impact of microstructural heterogeneities on the anisotropic evolutions in the microstructure and tensile properties during uniaxial tensile deformation of laser powder bed fused (LPBF-ed) IN718 superalloy in transverse (TD) and building (BD) directions. To quantify the effects of texture and geometrically necessary dislocations (GNDs), four model specifications were compared, including local (LSC) and non local (NSC) single crystal (SC) of specific grains, as well as local (LPC) and non local (NPC) polycrystal (PC) plasticity overall models. In-situ EBSD was conducted during tensile tests in TD and BD to validate the modeling outputs. Modeling results showed that TD loading produced a higher locally accumulated plastic slip and GND density at grain boundaries and slip bands, leading to greater overall dislocation strengthening than BD. GND density had a more significant effect on the deformation behavior in SC than PC models, while contributing more to strengthening in PC than in SC. The anisotropic and heterogeneous deformation in each grain mainly depended on its orientations in different directions, followed by the effects of PC texture and GND density. GND density had the highest hardening effects for <110>//loading direction (LD), followed by <111>//LD and <001>//LD grains. The highest yield strength belonged to <111>//LD grains, followed by <110>//LD and <001>//LD because of their ascending/descending Schmid factor/Taylor factor values. <212>//LD-oriented grains had the highest overall hardening slope, followed by <313>//LD, <111>//LD, <110>//LD, and <001>//LD directions.

Laser powder bed fusion (LPBF) additive manufacturing (AM) enables to three-dimensionally print intricate and customized high-end parts with a great promise for rapid manufacturing applications in aerospace, automobile, and medical industries. However, due to the lack of direct observations of defect formation and phase transformation dynamics, it suffers from keyhole pore residuals and heterogeneous phase structure as a result of repeated heating and cooling, which cause safety concerns and hinder wide industrial adoption. Here, we develop a miniature LPBF (mini-LPBF) setup that is flexible for in situ observations of keyhole and phase transformation dynamics through high-speed x-ray imaging and diffraction when implemented at synchrotron beamlines. The experimental validations of this mini-LPBF setup with an exemplary FeCoNiCrMn high-entropy alloy are carried out at BL16U2 and BL12SW beamlines of the Shanghai Synchrotron Radiation Facility. The subsurface transient dynamics of keyhole and phase transformation are characterized down to melt pool scale: keyhole geometry and its fluctuation induced pore formation are captured in high temporospatial resolution by high-speed imaging; phase transition from face-centered cubic, fully liquid and back to crystalline structures is quantified by time-resolved high-energy diffraction. This mini-LPBF setup provides the powerful infrastructure for keyhole fluctuation induced defect formation and phase transformation dynamics studies and experimental inputs for high-fidelity modeling. The knowledge gained by the aid of mini-LPBF setup through in situ monitoring of laser-metal interaction will improve the process stability and phase engineering for metal AM of novel alloys.

Based on the rotary bending loading principle, an experimental investigation into the fatigue properties of 6201 aluminum alloy individual wires is presented. Considering the long design service life, high-cycle fatigue (HCF) behavior, and slender geometry (high length-to-diameter ratio) of these wires, a high-speed rotary bending fatigue test platform is custom-designed and constructed. The design mechanically maximizes the probability of fracture at the midpoint of the constant-cross-section specimen, even when considering clamping damage at the ends. Through mechanical derivation for the test platform, based on the beam bending theory and the finite element method, a quantitative relationship is established between the bending stress amplitude and the deflection angle at the clamped end. Using this platform, the fatigue lives of 6201 aluminum alloy individual wires under various bending stress amplitudes are tested, and the stress–life (S-N) curve is obtained. The developed experimental method and the reported fatigue data in this study provide essential experimental and material data for fatigue life prediction and engineering design of 6201 aluminum alloy individual wires.

Superalloys have found broad applications in modern industrial aspects, especially in aerospace aspect, due to their superior mechanical properties. Investigations of microstructure evolution in superalloys during solidification, heat treatment and/or even service stages are critical and essential for optimizing processing techniques. Nowadays, PFM has become a powerful tool for studying microstructural evolution in superalloys, enabling the capture of complex phase transformations under realistic processing and service conditions. This paper systematically reviewed the recent advances of PFM applications in superalloys. Originating from thermodynamic formulations and kinetic equations, PFM has evolved into diverse models tailored to dendrite growth, precipitation evolution, creep and rafting behavior, and solute segregation. Recent advances in numerical techniques, including discretization schemes, Fourier spectral solvers, adaptive mesh refinement, and parallel acceleration, have greatly enhanced computational efficiency and accuracy. With these developments, PFM has been increasingly applied to casting, additive manufacturing, and heat treatment, enabling quantitative predictions of interface migration, stability of the γ′ phase, and defect formation. Nevertheless, challenges remain in parameter calibration, multi-physics coupling, and bridging across length and time scales, as well as propagating uncertainties from thermodynamic/kinetic databases, and establishing standardized benchmarks. Looking forward, the integration of AI with phase-field modeling is expected to enable intelligent model construction, adaptive simulation workflows, and multi-fidelity optimization, supporting more efficient microstructure–process–property linkage and accelerating alloy design and process optimization.

This research conducts a comparative study on the microstructure and mechanical properties of K4169 superalloy prepared by gravity casting (GC), counter-gravity casting (CGC) and laser powder bed fusion (LPBF). In the LPBF manufacturing process, the high temperature gradient and large cooling rate result in fine grains in the prepared samples (19∼30μm), as well as fine and distributed precipitated phases. This significantly improves their mechanical properties, which are far superior to those of the GC samples and slightly better than those of the CGC samples. The grain size of the CGC samples (650μm) is smaller than that of the GC (380μm) samples, and the size of the precipitated phases is also smaller, so their mechanical properties are better. After the three types of samples undergo SA (solution + aging) heat treatment, the molten pool in the LPBF samples disappears, the average grain size increases (45∼63μm), and a large number of δ phases and carbides precipitate at the grain boundaries, which reduces the plasticity of the LPBF samples. However, their mechanical properties reach the level of forged K4169. The grain size of the CGC samples does not change much, and more spherical carbides precipitate at the grain boundaries, which further improves the strength, making it close to that of the forged K4169 alloy, but the plasticity is further reduced. In the GC samples, there are still coarse and irregular Laves phases, acicular δ precipitated phases, and spherical carbides between the dendrites, and their strength is slightly improved. The analysis shows that the δ phase precipitated in the matrix after heat treatment reduces the plasticity of the K4169 while improving the strength of the material.

A comprehensive understanding of defect-microstructure-property relationships is essential for advancing additively manufactured aluminum alloys. In this study, an Al-9.5Ce-0.5Si-0.6 Mg alloy was fabricated by laser powder bed fusion (L-PBF). In-situ X-ray computed tomography (XCT), combined with multi-scale microstructural characterization, revealed distinct defect-dependent damage mechanisms. Irregular lack-of-fusion (LOF) pores generated severe localized stress concentrations and served as dominant crack initiation sites, whereas small spherical gas pores exhibited isolated volumetric growth with negligible contribution to catastrophic failure. By tailoring processing parameters, LOF porosity was effectively suppressed while promoting a microstructural transition from columnar to fine equiaxed grains, coupled with interconnected nanoscale alpha-Al + Al11Ce3 eutectic networks. In the absence of severe LOF defects, damage evolution is dictated by intrinsic microstructural heterogeneity, where coarser eutectic networks at melt pool boundaries (MPBs) drive pronounced strain localization and govern final failure. Benefiting from the synergy of LOF pore suppression and microstructural refinement, the optimized L-PBF Al-Ce-Si-Mg alloy achieves a superior strength-ductility balance, with a yield strength of similar to 285 MPa, an ultimate tensile strength of similar to 427 MPa, and an elongation to fracture of similar to 7%, significantly outperforming most reported L-PBF Al-Ce alloys. These findings clarify the roles of porosity and microstructural heterogeneity in damage evolution and provide mechanistic guidance for the design of high-performance additively manufactured aluminum alloys.

Localized corrosion in multiphase aluminum alloys is governed by micro-galvanic coupling between intermetallic phases and the Al matrix. Here, an Al-Ce-Mg alloy containing an in-situ Al11Ce3 nano-network was fabricated via laser powder bed fusion to clarify the role of intermetallic morphology in corrosion behavior. Electrochemical measurements show that the as-built alloy exhibits an order-of-magnitude lower corrosion current density and higher polarization resistance than the heat-treated alloy. Scanning Kelvin probe force microscopy reveals that the nano-network reduces the potential difference between Al11Ce3 and the Al matrix from ∼111 mV to ∼26 mV. Meanwhile, XPS and TEM analyses reveal the formation of a compact CeO2-rich passive film that suppresses micro-galvanic corrosion and enhances corrosion resistance.

Severe intergranular oxidation and microstructural instability remain major challenges limiting the extensive applications of structural alloys at elevated temperatures. In this study, we propose an innovative strategy by developing a chemically complex intermetallic alloy (CCIMA) based on the L1(2)-type Co-Ni-Al-Ti-Nb-Ta-B system. This alloy design incorporates a thermally stable, Co-rich disordered interface nanolayer (DINL) with a face-centered-cubic (FCC) structure, which effectively mitigates these critical issues. The newly developed CCIMA demonstrates exceptional microstructural stability, maintaining its ordered L1(2) matrix and DINLs after the long-term exposure for 336 h at 1000 degrees C. Grain size remains stable at similar to 30 mu m due to the DINL-induced reduction in the grain-growth driving force. Nanoscale on-axis Transmission Kikuchi Diffraction (TKD) and transmission electron microscopy (TEM) analyses reveal a four-layer oxide-scale comprising NiCo2O4, CoAl2O4, a mixed layer of (TiNbO4+Al2O3+AlTaO4), and an inner Al2O3 layer. The compact and nanocrystalline morphology of these oxides confers superior oxidation resistance. Notably, intergranular oxidation and the formation of a degradation layer at the alloy/oxide interface occur only within the initial 2 min of oxidation, after which the material exhibits a unique self-healing effect. Supported by density functional theory (DFT) calculations, the underlying atomic mechanism governing this self-healing behavior was unveiled. The present work would provide new insights into the alloy-design strategies for the development of next-generation high-temperature materials with superior structural and oxidation resistance.