Dimensional deformation and shrinkage porosity are key investment casting defects that typically occur during solidification of the casting at ambient environment after high-temperature pouring. Although these two indicators are caused by various reasons, it is believed that the initial temperature of the shell is one of the dominant factors. This study leverages experiment and simulation methods to reveal the relationship between the temperature drop of ceramic shells and the dimensional deformation and shrinkage porosity of castings in CoCrMo alloy investment casting joints. The experimental results indicate that the insulation conditions of ceramic shells and the filling of high-temperature melt have a significant impact on the temperature drop curve of ceramic shells. The temperature drops of ceramic shells insulated with asbestos are much slower than that of ceramic shells without asbestos insulation, which has a significant impact on the dimensional deformation and shrinkage porosity of castings. Numerical simulation was conducted using a model calibrated for ceramic shell temperature, and the results showed that with the shell preheating temperature increasing from 800 to 1000 °C, the total shrinkage volume in the casting decreased from 4.19 to 2.38 cm3, the total displacement of the casting decreased from 1.2 to 1.0 mm, and the gap width decreased from 0.774 to 0.651 mm.

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.

Gallium-based liquid metals possess high electrical conductivity and fluidity, but their enormous surface tension makes it difficult to disperse them uniformly in aqueous media. In this work, five types of nanocellulose, namely, cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), TEMPO‑oxidized cellulose nanofibrils (TCNFs), quaternized cellulose nanofibrils (QCNFs), and bacterial cellulose (BC), were compared as interfacial stabilizers for gallium liquid metal (LM) Pickering emulsions. The nanocellulose/liquid metal Pickering emulsions were prepared by probe ultrasonication and characterized by optical microscopy, dynamic light scattering/zeta potential, TEM, FTIR, XPS, and TGA. All nanocellulose/liquid metal droplets formed core–shell structures, suppressing droplet coalescence. The stability of nanocellulose stabilized liquid metal Pickering emulsions followed the order BC > TCNFs > CNFs > QCNFs > CNCs. XPS analyses revealed that functional groups on nanocellulose interact with the gallium oxide skin via electrostatic attraction and coordination, and TGA indicated that the composites maintain good thermal stability and form gallium oxide at high temperatures. These results demonstrate that renewable nanocellulose can serve as green and effective stabilizers for high‑surface‑energy liquid metal, enabling long‑term stable Pickering emulsions.

NiCo–LDH@ZnSe possesses a unique layered structure with abundant active sites, demonstrating outstanding theoretical capacitive performance.

Nano-SiC/Al-Zn-Mg-Cu composites are prepared by high-energy ball milling combined with spark plasma sintering （SPS） and hot extrusion. The precipitation hardening characteristics， aging precipitation behavior， and microhardness of nano-SiC/Al-Zn-Mg-Cu composites are studied by differential scanning calorimetry （DSC）， synchrotron radiation X-ray diffraction（SR-XRD）， transmission electron microscopy （TEM） analysis and microhardness test. Results show that the addition of nano-SiC particles increases the thermal diffusion activation energy of η'and η phases， and inhibits the growth of the precipitated phase in the composites. Moreover， adding SiC particles increases the concentration of η' phase and refines the η phase at the grain boundaries， which enhances the precipitate-strengthening effect. With the increase of aging time， the density and size of η' phase within the grain increases， and gradually transforms into η phase. Meanwhile， the η phase precipitated along the grain boundary coarsens. Increasing the aging temperature can increase the free energy of the composite system and the diffusion rate of the solute atoms， promoting the growth of η' phase and η phase and the transformation of η' to η phase. The addition of 3%（volume fraction）SiC nanoparticles increases the microhardness by about 50%， and the peak aging time decreases from 64 h to 16 h with the aging temperature increasing from 100 ℃ to 140 ℃， but the aging temperature change has little effect on the hardness value of peak aging.

To elucidate the interplay between the dual-phase structure and mechanical behavior of discontinuous precipitation (DP), in-situ synchrotron X-ray diffraction (SRXRD) is performed on the Al-22 at.% Zn model alloys during uniaxial tensile loading. The results reveal that DP plays a key role in reducing texture development in the alloy. A small amount of DP induces splitting of Al diffraction peaks, reflecting localized stress at the Al/Zn coherent interface caused by lattice mismatch. Increased DP content correlates with reduced maximum lattice strain, suggesting the mitigation effect of DP on local stress concentration. A quantitative method for analyzing lattice rotation from 2D SRXRD data is developed and applied to investigate the deformation mechanisms related to the rotation of DP. The results reveal that trace DP at grain boundaries suppress intragranular rotation, leading to localized lattice torsion, while the overall and relative rotations of DP lamellae induce localized plastic flow. Besides, the alternating lamellar structure of the DP effectively restricts the dislocation motions, suggesting a greater reliance on lattice rotation over dislocation motion during plastic deformation, which led to an improvement in ductility. The exploration of the new deformation mechanisms in DP-containing alloys, specifically lattice rotation behavior, provide theoretical guidance for performance prediction and offering insights into achieving strength-ductility synergy via manipulations of DP structure.

Al-Zn based alloys with high Zn content are limited in practical applications due to low ductility. Introducing discontinuous precipitation (DP) into the alloy offers a promising route to optimize the mechanical properties. This paper takes Al-22 at% Zn as a model alloy to study the precipitation behavior, delineating innovative strategies for the improvement of mechanical properties. Through appropriate treatment, the volume fraction of DP in this alloy can reach about 90 %. The DP microstructure of this alloy is composed of lamellar Al and Zn phase arranged in layers. As a precipitation mode competing with DP, continuous precipitation exists in this alloy in the form of granular Zn precipitates, with the precipitation-free zone (PFZ) located at the interface between these two precipitated structures. Electron Backscattered Diffraction results suggest that the introduction of DP into the alloy reduces local stress concentrations within the microregions, which could account for the observed increase in ductility with the increase in DP content. The presence of PFZ induces the accumulation of dislocations and exerts an adverse influence on the ductility of the alloy. Variations in the PFZ content serve as a significant factor contributing to changes in alloy strength.

Developing cost-effective magnesium alloys with superior mechanical properties is critical for advancing largescale industrial applications. This study presents a high-performance Mg-6Zn-1Mn-3Sn-xSm alloy fabricated through trace Sm addition and two-step aging optimization. Systematic investigations reveal that incremental Sm content refines the MgSnSm phase (reduced size, increased volume fraction). Through a tailored heat treatment process, the Mg-6Zn-1Mn-3Sn-0.5Sm alloy achieves exceptional strength with an ultimate tensile strength (UTS) of 418 MPa and a yield strength (YS) of 328 MPa. The MgSnSm phase has an orientation relationship with the R ' phase, which can act as a heterogeneous nucleation particle to promote the precipitation of the R ' phase during aging. Superior performance stems from the combined effects of the MgSnSm phase dispersion strengthening and high-density R' precipitation hardening. This work provides a strategic pathway for designing high-strength magnesium alloys with minimal rare-earth (RE) additions.

Heterogeneous structure significantly impacts the applications of wrought magnesium (Mg) alloys. Herein, we put forward a novel idea for constructing the heterogeneous structure by utilizing solute grain boundary (GB) segregation on recrystallization behavior during hot extrusion. The formation of heterogeneous structure is primarily attributed to the solute drag pressure (Al, Zn, and Ca), increasing solute atom levels co-segregation in GB, and the activation of non-basal dislocations, which contribute to hindering continuous dynamic recrystallization. This study highlights the multi-scale solute atom GB segregation behavior and provides new insights into GB segregation-induced heterogeneous structural transition in Mg alloy.

The development of low-cost and high-performance Mg alloys is an important way to achieve further application of magnesium alloys. In this work, the as-extruded Mg98.3-xZnxGd1Sm0.7 alloy with excellent mechanical properties is successfully prepared by regulating the bimodal-grained structure. The effect of the Zn content on the microstructure evolution and mechanical properties of the as-extruded Mg98.3-xZnxGd1Sm0.7 alloy is systematically investigated. The results show that the addition of Zn increases the dynamic recrystallization (DRX) fraction and weakens the basal texture of the as-extruded alloy. The Mg98.05Zn0.25Gd1Sm0.7 alloy exhibits a typical bimodal-grained structure. A large amount of geometrically necessary dislocations (GNDs) are generated at the interface between the soft zone and the hard zone of the bimodal-grained structure during the plastic deformation process, resulting in back stress strengthening, thereby improving the strength of the alloy. And it achieves exceptional mechanical properties with an ultimate tensile strength (UTS) of 330 MPa, a yield strength (YS) of 248 MPa, and an elongation (EL) of 18.5% at room temperature. This paper provides a new idea for introducing a heterogeneous structure and improving the strength of low-cost Mg alloys.

GTD 111 has been employed in first-stage blades in different gas turbines. The study of microstructural evolution is essential for the lifetime assessment and development of turbine blades. The microstructural stability of a 130 MW gas turbine first-stage blade at 800 °C was studied. The microstructure’s evolution was analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic calculation. As thermal exposure time increases, the shape of γ′ precipitates changes from square to spherical. During thermal exposure, MC particles formed and coarsened along the grain boundaries, and primary MC carbide decomposed into the η phase and M23C6. The stability of MC carbide at the grain boundaries was lower than that within the grains. MC carbide precipitated at the grain boundaries tends to grow along the boundaries and eventually forms elongated carbide. High-resolution transmission electron microscopy (HRTEM) images indicate that the orientation of the γ′ precipitate changes during the coarsening process. The GTD 111 alloy can be deformed through dislocation shearing at 800 °C. The hardness value initially increases, then decreases with further exposure, which is related to the reduced precipitation strengthening by γ′ precipitates and the reduction in the hardness of the γ matrix.

The development of heterogeneous metal material is the key issue in improving the absolute strength of low-alloyed magnesium (Mg) alloys. In the present work, a novel lamellar heterogeneous low-alloyed Mg-1.2Al-0.6Ca-0.4Zn alloy with strength-ductility synergy was developed by the traditional extrusion process. The results demonstrate that regulating the proportion of soft-zone and hard-zone grains via various Zn additions plays a key role in constructing the lamellar heterogeneous structure. The Mg-1.2Al-0.6Ca-0.4Zn alloy exhibits a lamellar heterogeneous characteristic with the proportion of soft/hard zone grains of 7: 3, which provides a remarkable synergistic improvement of strength and ductility compared with the uniform structure Zn-free Mg-1.2Al-0.6Ca alloy. During the deformation process, numerous dislocations arise from the soft/hard interface, and the dislocations bypassed by nanoscale rod-like Al2Ca precipitates predominantly formed at deformed grain induce geometrically necessary dislocations (GNDs) to accommodate the strain, which offers hetero-deformation induced (HDI) hardening to enhance the strength of AX-0.4Zn alloys.

Microstructure evolution and cracking behavior of a four-layer thermal barrier coating (TBC) with double YSZ layers during thermal cycle tests were studied in the current work. The temperature range of the thermal cycle test ranged from room temperature to 1100 °C under atmospheric conditions. The TBC consisted of tetragonal t′ and t phases as well as monoclinic yttrium oxide. After 500 thermal cycles, the m-ZrO2 phase was formed through the phase transformation from t′-ZrO2 to m-ZrO2 and c-ZrO2. A large number of bulk thermally grown oxides (TGO), including chromium, spinel, and yttrium aluminates, were formed around pores in the transition layer (TL). Furthermore, the thickness of the TGO layer increased with a relatively low increase rate during the test (where kp was about 0.17 μm2/h). This may be attributed to the formation of bulk TGO around pores within the TL, which could consume some of the oxygen. The results show that large horizontal cracks are likely to form at the TSL/TIL and TIL/TL interfaces, while vertical cracks tend to occur near the surface of the TSL, and the propagation rate is relatively low. The propagation of horizontal cracks is the primary cause of failure in this four-layer structure. After the thermal cycle test, the porosity of TSL decreased significantly, from 7.17% to 0.76%. The results in this study may help optimize the design and preparation of TBCs with double YSZ layers.

Dissimilar joining of NiTi and stainless steel (SS) is important in biomedical applications but poses significant challenges due to brittle intermetallic compounds (IMCs) formation in the welds. Replacing harmful phases in fusion welding cannot fully eliminate brittle IMCs and may introduce toxic elements, while the mixing restriction in solid-state welding increases the process complexity and results in large plastic deformation that degrades NiTi functional properties. In this work, we present a novel methodology that achieves a solid-state joined interface in NiTi-SS fusion welding (i.e., resistance microwelding) through in-situ interfacial liquid control. By combining the advantages of both welding techniques, the current method produced NiTi-SS joints with superior strength, superelasticity and biocompatibility compared to NiTi joints or base metal. The ultrathin reaction layer at the solid-state joined interface contributed to a strong metallurgical bonding, while Joule heating effects and interfacial reactions enhanced superelasticity and biocompatibility of the joint. By demonstrating complete superelasticity on NiTi side, flexible deformation capacity on SS side, superior resistance to hydrogen embrittlement and electrochemical corrosion, and reduced Ni ion release and cytotoxicity, the welded joint shows great potential for the fabrication of multifunctional biomedical devices. Our work not only provides a comprehensive study of NiTi-SS joining under the biomedical background, but also introduces a new strategy for controlling material interface and dissimilar-metal welding process. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Enhancing homogenization efficiency and hot-workability is the key issue for wrought superalloys in the industry.A novel approach for simultaneous accelerating the homogenization kinetics and improving hot-workability via a simple way of prior hot-deformation was proposed,which was not widely accepted for wrought superalloys.The homogenization effi-ciency is increased by 40％-70％via performing 10％-20％prior hot-deformation.Both theoretical and experimental analyses revealed that the increment in homogenization efficiency is mainly attributed to the decrease in interdendritic-segregation spacing,and thus the necessary diffusion distance,rather than that of dislocations.In addition,dynamic and static recrystallizations occurred during the prior hot-deformation and diffusion-annealing processes,and the grains were significantly refined even after the homogenization.Furthermore,the size of the precipitates was refined as well.These enhanced the hot-workability of the homogenized ingot for the subsequent cogging process.

Aging treatment plays a significant role in altering the mechanical properties of superalloys; however, the influences of aging on the mechanical performance of Rene 41 alloy and its strengthening mechanisms remain unclear. In this study, the effects of aging on the microstructure and mechanical properties of forged Rene 41 alloy were systematically investigated through experimental and theoretical analyses. It was found that aging conditions have significant influences on the grain structure, γ′ characteristics, and tensile properties of the alloy. The size of secondary γ′ increased from 20 nm to 69 nm with elevated aging temperature and prolonged aging time, while their volume fraction initially increased and then decreased. Notably, the γ′ maintained a coherent interface with the matrix even after high-temperature aging at 860 °C. An optimal strength–ductility balance was achieved by aging at 760 °C for 16 h. An experimentally verified strengthening model was used for understanding the strengthening mechanisms of the alloy aging at varying conditions. Precipitation strengthening was identified as the dominant strengthening mechanism, substantially contributing to the overall yield strength. The precipitation strengthening mainly belongs to the strong pair-coupling cutting mechanism rather than the Orowan bypass mechanism. This study concludes that a rational aging treatment regime can significantly optimize the comprehensive properties of Rene 41 alloy, providing theoretical support for its application in aerospace component manufacturing.

Laser direct energy deposition (LDED) offers unique advantages in the integrated forming of 3D complex-shape parts. However, the columnar grains that grow epitaxially along the building direction are prone to reduce the performance of the as-built parts. Herein, external ultrasonic field are introduced during the LDED of near-alpha titanium alloy Ti60 (Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C), resulting in equiaxed beta grains with an average grain size of 62.82 mu m. The single track morphology, molten pool, microstructure, and mechanical properties under different ultrasonic powers are characterized and investigated. The results indicate that the ultrasound can induce columnar to equiaxed transition (CET) of the prior-beta grains and promote the precipitation of silicides, but the width of the alpha laths increases due to heating effect caused by ultrasound. Consequently, the sample prepared with the 6 mu m ultrasonic vibration exhibits a increases of 67.18 % in elongation, and the mechanical properties reach the forge standard. Finally, the effects of prior-beta grain and alpha lath on the final mechanical properties of the samples are discussed. This work provides a deep insight into the LDED process of near alpha titanium alloy Ti60 assisted with ultrasound.

The incorporation of nanoparticle reinforcements into high-entropy alloy (HEA) has proven effective in improving the strength of face-centered cubic HEAs. However, this often results in a substantial loss of ductility. While a balance between strength and ductility can be achieved through multiple deformation mechanisms, these are typically triggered by extreme deformation conditions or by chemical composition manipulation. This study explores an alternative approach through heterogeneous microstructure architecture to activate multiple deformation mechanisms. Heterogeneities such as heterogeneous grains and nanoprecipitates were introduced into an in-situ synthesized Al2O3 nanoparticles reinforced CoCrFeNiAl0.3 HEA nanocomposite via powder metallurgy and thermomechanical treatment processes. The research investigated the strengthening mechanisms and deformation behaviors under both quasi-static and dynamic deformation. Results revealed that the engineered heterogeneities facilitated multiple deformation behaviors. Stacking faults formed in ultrafine grains, while deformation twins and microbands formed in fine grains during quasi-static tension. Under dynamic compression deformation, dislocation cells, stacking fault networks, deformation twinning and HCP phase transformation occurred in fine grains. These mechanisms endowed the CoCrFeNiAl0.3 HEA nanocomposite with exceptional mechanical performance, achieving a true stress of 1595 MPa and a true strain of 45.1%. The enhanced stress-strain response prolonged the evolution of dislocation activities, ultimately enabling the transition from dislocation-microband interaction to the formation of dislocation cells.

GH4141 wrought superalloy is widely used in the manufacture of high-temperature load-bearing components for aerospace engines due to its high strength and good oxidation resistance at high temperatures. In this paper, based on chemical composition analysis and crystallographic method, the typical precipitates in the as-cast GH4141 alloy were identified and analyzed. The dissolution behaviors of the precipitates during the homogenization process were analyzed through the high-temperature homogenization experiments. The results show that under the medium and low temperature homogenization conditions of 1130-1160 degrees C, the needle-like sigma phase, plate shape eta phase, M3B2 boride and gamma ' strengthening phases of the original as-cast structure are dissolved into the matrix, while the M6C carbides still exist. Under the condition of high temperature homogenization at 1190-1210 degrees C, most of the precipitates including M6C in the alloy have been dissolved into the gamma matrix, and only small part of MC carbides remain in the structure. Besides, it's worth noting that the MC carbides are dissolved in the solid-liquid two-phase region, and the MC carbides are difficult to be completely dissolved and eliminated through homogenization heat treatment.

This article combines X-ray diffraction (XRD) analysis of limestone after high-temperature treatment with microscopic structural characteristics. It aims to elucidate the changes in diffraction peak characteristics from a microscopic perspective and investigate the thermodynamic property variations of the material. The research findings indicate that 500 degrees C is the threshold temperature at which limestone's crystalline orientation and spatial arrangement change, resulting in a decrease in peak height in the diffraction pattern. Additionally, temperatures ranging from 500 to 600 degrees C accelerate particle thermal motion, leading to the detachment of rock layers, the inward extension of fissures, and the formation of a sedimentary rock-like 'layered' stacking structure. The thermal conductivity, specific heat capacity, and heat storage coefficient of limestone gradually decrease after thermal treatment, with a reduction rate of approximately 3 % per 100 degrees C. The microstructural characteristics and thermodynamic property changes of high-temperature limestone reveal the impact of high-temperature damage on limestone structure and thermodynamic properties, facilitating the advancement of limestone material applications and damage control under high-temperature conditions.