Effect of metastability on non-phase-transformation high-entropy alloys

Abstract

The development of an effective strategy to improve the elastic performance of non-phase-transformation high-entropy alloys (HEAs), as well as the investigation on the effect of metastability on HEAs, is of great significance both practically and theoretically. The structure, morphology and mechanical properties of the HfZrTiTa (HZTT) alloys quenched from 873 K to 1573 K were studied systematically. Results revealed that the HZTT HEAs composed of two coherent BCC structures was in a metastable state. Dispersed nano-lamellar modulated structure inside the equiaxed grains was derived from spinodal decomposition. The dependence of the width of the stripe on quenching temperature is controlled by the uphill diffusion of the constituent elements, while the variation of the lattice distortion is in accordance with Logistic model. The mechanical properties of the HZTT HEAs, including hardness, yield strength, elastic modulus and elastic limit strain, are regulated by metastability from the perspectives of lattice distortion and bonding energy. The yield strength and the elastic limit strain of the HZTT HEAs can reach 1.78 GPa and 3.1%, respectively, by increasing the quenching temperature and improving the metastability of the alloys. The as-prepared alloys are promising candidates in the application field of high-strength damping bearings. Keywords: High-entropy alloy, Metastability, Elastic deformation, Spinodal decomposition, Non-phase-transformation, High-strength damping bearings