Zr alloying effects on the microstructure, compression performance and oxidation resistance of refractory high entropy alloys

Abstract

Three refractory high entropy alloys (RHEAs) with nominal compositions of Mo0.5NbHf0.25CrZrxTiAl (x = 0, 0.5, 1, mole ratio) were prepared by vacuum non-consumable arc melting technology. The influences of Zr addition on the microstructure, compressive performance and oxidation resistance at 1473 K of RHEAs were investigated and evaluated integrally. The results show that the three RHEAs are all composed of BCC1, BCC2 and Laves phases. With increasing the Zr content, the microstructure of RHEA has gradually become BCC1 + BCC2 eutectics, and also the area fraction of BCC2 phase exhibits a rising trend. Both peak stresses are displayed at the strains of near 0.03 and 0.08 respectively in the compressive stress-strain curves of the three RHEAs. On the whole, the compressive yield strength of RHEA shows an increasing trend with Zr addition. The oxide scales of the three RHEAs all possess good adhesion and obviously layered structures. The different oxidation products are distributed in their oxide scales and internal oxidation zones. The oxidation resistance of RHEA is dramatically degraded due to the decreased compactness of the oxide scale with Zr addition.