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。

Microstructure and Mechanical Properties of TiVNbTa Refractory High-Entropy Alloy Prepared by Powder Metallurgy

The TiVNbTa refractory high-entropy alloy (HEA) was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The mechanically alloying process, phase composition and microstructure as well as the effect of sintering temperature, O- and N-content on the mechanical properties of the alloy were studied. The mechanically alloyed powders present a single BCC crystal structure, while the spark plasma sintered alloy composed of a FCC matrix with precipitated phases of TiN, TiC and TiO. The alloy sintered at 1100°C performed outstanding mechanical properties with compressive yield strength of 1506 MPa and plastic strain of 33.2%, respectively. As sintering temperature increased, the alloy fracture mechanism basically transformed from quasi-brittle fracture to ductile fracture, and finally to brittle fracture. The increase of O- and N-content had little effect on the strength of the alloy, but negative effect obviously on its plasticity.