粉末冶金TiVNbTa难熔高熵合金的组织和力学性能

将机械合金化(MA)与放电等离子烧结(SPS)相结合制备了难熔TiVNbTa高熵合金,研究了这种合金的机械合金化过程、相组成和显微组织,以及烧结温度和O、N含量对其力学性能的影响。结果表明:机械合金化后高熵合金粉末为BCC结构,放电等离子烧结成的块体高熵合金由BCC基体和FCC析出相组成,其析出相为TiN+TiC+TiO的复合物。烧结温度为1100℃的高熵合金具有良好的综合力学性能,压缩屈服强度达到1506.3 MPa,塑性应变为33.2%。随着烧结温度的提高,合金发生了从准脆性到塑性再到脆性断裂的转变。O和N含量的提高对高熵合金强度的影响较小,但是使其塑性显著降低。     

新型含Cu高熵合金的微观组织及热处理过程相变

目的为优化CrMnFeCoNi高熵合金成分,消除富Cr脆性相的析出倾向。方法用Cu取代Cr元素,以四元MnFeNiCu高熵合金为研究对象,探究含Cu高熵合金的微观组织及其热处理过程中的相变特征。结果铸态MnFeNiCu合金中Cu元素具有较强的偏析倾向,其枝晶间存在大量颗粒状富Cu析出物,通过均匀化热处理能完全消除Cu元素偏析现象,得到单相FCC组织。结论 Cu与其他3种元素均表现为不同程度的不相容性,具有最大的偏析倾向,使其在凝固过程中于枝晶间富集,均匀化热处理过程中Cu元素发生溶质扩散,最终形成了单相固溶体组织。     

多主元高熵合金的研究进展

多主元高熵合金突破了以1种或2种金属元素为主的传统合金的设计理念,是一种有5种以上主元且每种主元原子百分数不超过35%的新型合金.高熵合金显现出许多不同于传统合金的组织和性能特点,是具有学术研究价值和工业应用潜力的材料领域.重点介绍了高熵合金的定义、组织和性能特点与研究状况.     

Effects of Fe/Ni Ratio on Microstructure and Properties of FeNiCrAlNb High-Entropy Alloys

Herein, the effects of Fe/Ni ratio on the microstructure, mechanical properties, and corrosion resistance in a 3.5 wt% NaCl solution of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ are investigated systematically. It is found that the phases shifted from the FCC-dominated to the BCC-dominated with the molar ratio of the Fe/Ni increased. The strength of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ increases with the molar ratio of Fe/Ni further increased, while the plasticity decreases. The yield strength reaches 1,653 MPa at x = 45. The alloy exhibits the best corrosion resistance when x = 35 which is attributed to the dominant FCC phases in the dendritic region.     

沉淀强化镍基合金屈服强度的理论计算EI

本文提供了依据合金的化学成分、显微组织参数定量计算合金屈服强度性能的理论方法。具体计算了一组镍基合金的室温屈服强度，计算值与实测值很好地符合。     

Beating Thermal Coarsening in Nanoporous Materials via High-Entropy Design

Controlling the feature sizes of 3D bicontinuous nanoporous (3DNP) materials is essential for their advanced applications in catalysis, sensing, energy systems, etc., requiring high specific surface area. However, the intrinsic coarsening of nanoporous materials naturally reduces their surface energy leading to the deterioration of physical properties over time, even at ambient temperatures. A novel 3DNP material beating the universal relationship of thermal coarsening is reported via high-entropy alloy (HEA) design. In newly developed TiVNbMoTa 3DNP HEAs, the nanoporous structure is constructed by very fine nanoscale ligaments of a solid-solution phase due to enhanced phase stability by maximizing the configuration entropy and suppressed surface diffusion. The smallest size of 3DNP HEA synthesized at 873 K is about 10 nm, which is one order of magnitude smaller than that of conventional porous materials. More importantly, the yield strength of ligament in 3DNP HEA approaches its theoretical strength of G/2π of the corresponding HEA alloy even after thermal exposure. This finding signifies the key benefit of high-entropy design in nanoporous materials—exceptional stability of size-related physical properties. This high-entropy strategy should thus open new opportunities for developing ultrastable nanomaterials against its environment.     

Carbon Segregation in CoCrFeMnNi High-Entropy Alloy Driven by High-Pressure Torsion at Room and Cryogenic Temperatures

Herein, a CoCrFeMnNi high-entropy alloy with reduced Cr content and with the addition of 2 at% C interstitial is processed via high-pressure torsion (HPT) under 6.5 GPa by three turns at room and cryogenic temperatures. The microstructure is investigated by transmission electron microscopy (TEM) and atom probe tomography (APT). The results indicate that C atoms segregate at the boundaries of the nanograins in the sample processed at room temperature, while the sample processed at cryogenic temperature does not show any notable segregations of carbon.     

Ultrastrong High-Ductility Ni35Co35Fe10Al10Ti8B2 High-Entropy Alloy Strengthened with Super-High Concentration L12 Precipitates

L1₂ phase hardening alloys with excellent mechanical properties are of great significance for structural applications. However, low volume fractions of L1₂ precipitates in conventional alloys (nearly lower than 60%) tend to limit their practical usage, while the strengths of the alloys generally increase with L1₂ precipitation contents. Herein, a novel high-entropy alloy (HEA) Ni₃₅Co₃₅Fe₁₀Al₈Ti₁₀B₂ with ultrahigh concentration L1₂ precipitates is successfully designed aided by the calculation of phase diagrams (CALPHAD). The volume fraction of L1₂ precipitates in this HEA is up to 75% and outperforms that of most of traditional superalloys. The novel L1₂-strengthened Ni₃₅Co₃₅Fe₁₀Al₈Ti₁₀B₂ has an ultrahigh tensile yield strength of ≈1.45 GPa, ultimate tensile strength of ≈1.9 GPa, and great ductility of ≈23% at room temperature. The desirable strength–ductility combination is superior to most of conventional superalloys and reported HEAs, mainly due to the presence of ultrahigh concentration L1₂ precipitates that act as dislocation obstacles and the formation of numerous stacking faults and deformation twining. This work is expected to provide guidance for developing new high-performance HEAs with an excellent combination of strength and ductility.     

Hybrid Nanostructures and Stabilized Mechanical Properties of High-Entropy Alloy Induced by Warm Laser Shock Peening

Recently, the manufacture of high-entropy-alloy (HEA) parts by selective laser melting (SLM) has been extensively studied. However, the problems of high tensile residual stress, undesirable microstructure, and unstable mechanical properties in HEA parts caused by SLM process are difficult to be solved simultaneously. Herein, a warm laser shock peening (WLSP) process is used to obtain high strength, stable mechanical property, and favorable residual stress in SLMed FeNiCrCo HEA by regulating the microstructure in material. Experimental and simulation results show that WLSP treatment can induce high-density dislocations and nanotwins in the HEA, resulting in a 39.4% increase in the surface strength of the HEA. Moreover, because of the high atomic kinetic energy brought by high temperature in WLSP processing, WLSP-treated sample has higher density of dislocations and nanotwins than the sample treated by the LSP process at room temperature (RLSP), resulting in higher surface strength and better mechanical stability of the WLSP-treated HEA. Meanwhile, the WLSP treatment enables the tensile residual stress generated in the SLM process to be transformed into compressive residual stress, which can enhance the fatigue performance of the HEA. Therefore, WLSP has great potential in obtaining SLMed HEAs with excellent mechanical properties.     

难熔高熵合金的研究进展及应用

高熵合金不同于传统工程合金,是由多种元素以等摩尔或近等摩尔的比例混合,形成的以简单固溶体结构为基体的系列成分复杂合金。其中含高熔点元素的难熔高熵合金具有较高的高温强度和优异的高温抗氧化性能及耐蚀性能等突出特点,其潜在的高温应用价值引起了广泛关注。详细阐述了难熔高熵合金的研究现状及应用,根据晶体结构类型将难熔合金体系进行了分类,并对各类体系中的微观组织特征进行了概述;进而归纳总结了难熔高熵合金的各种性能,包括高强度、耐磨性、高温抗氧化性、耐蚀性能等;最后对难熔高熵合金的发展及应用前景进行了展望。     

陶瓷颗粒增强Cr0.5MoNbWTi难熔高熵合金复合材料的制备及其力学性能

难熔高熵合金因其优异的力学性能、高温稳定性和抗氧化性能等,作为高温结构材料具有广阔的应用前景.为了进一步提升材料的力学性能,本研究利用原位反应烧结制备了陶瓷颗粒增强难熔高熵合金复合材料,并探讨了陶瓷增强相的生成机理及其对复合材料力学性能的影响.通过机械合金化制备了含有碳氮氧非金属元素的Cr0.5MoNbWTi过饱和体心...