Hf含量对NbMo0.5HfxTiZrCrAl难熔高熵合金组织及力学性能的影响

Effect of Hf content on microstructure and mechanical properties of NbMo0.5HfxTiZrCrAl refractory high-entropy alloy

摘要:

采用真空非自耗电弧熔炼的方法制备了5种名义成分为NbMo0.5HfxTiZrCrAl(x=0, 0.25, 0.5, 0.75, 1, at.%)的难熔高熵合金。研究了Hf对合金组织及力学性能的影响规律。结果表明：添加Hf和不添加Hf的合金的微观组织均由两种BCC相（即BCC1和BCC2）和Laves相构成。在未添加Hf的合金中，BCC1相中主要富含Zr、Cr和Al元素，BCC2相中主要富含Nb、Ti和Mo元素。而在添加Hf的合金中，BCC1相中主要富含Hf、Zr、Cr、Mo和Al元素，BCC2相中主要富含Nb和Ti元素。随着Hf含量的增加，BCC1相的含量逐渐增加，且BCC1和BCC2相的晶格常数均有所增大。此外，随着Hf含量的增加，合金的硬度和脆性均逐渐增加，而合金在1200 ℃的抗压强度逐渐降低。

Abstract:

Five refractory high-entropy alloys with nominal composition of NbMo0.5HfxTiZrCrAl (x=0, 0.25, 0.5, 0.75, 1, at.%) were prepared by vacuum non-consumable arc smelting. The effects of Hf addition on the microstructure and mechanical properties of the alloys were studied. The results show that the microstructures of the alloys with and without Hf are composed of two BCC phases (namely BCC1 and BCC2) and Laves phase. In the alloy without adding Hf, the BCC1 phase is mainly rich in Zr, Cr and Al elements, and the BCC2 phase is mainly rich in Nb, Ti and Mo elements. In the Hf-added alloys, the BCC1 phase is mainly rich in Hf, Zr, Cr, Mo and Al elements, and the BCC2 phase is mainly rich in Nb and Ti elements. With the increase of Hf content, the amount of BCC1 phase gradually increases, and the lattice constants of BCC1 and BCC2 phases both increase. In addition, with the increase of Hf content, the microhardness and brittleness of the alloy gradually increase, and the compressive strength of the alloy at 1200 ℃ gradually decreases.