A low-density high-entropy dual-phase alloy with hierarchical structure and exceptional specific yield strength

Abstract

A high-entropy dual-phase AlTiVCoNi alloy with a low density of ∼6.24 g cm−3 is developed, and it consists of a hierarchical structure, including an ordered L21 phase, a disordered body-centered-cubic (BCC) solid-solution phase, and nano-sized L21 precipitates embedded in the BCC phase. It is found that this new alloy shows phase stability after the heat treatment at 1200°C for 24 h, and the compressive yield strength of this annealed alloy is approximately equal to that of the as-cast condition, ∼1.6 GPa. This alloy displays an exceptional compressive strength at room temperature and at 600°C, with the specific yield strengths of ∼261 and ∼210 MPa g−1 cm3, respectively. The semi-coherent interface of the L21 and the BCC phases makes the alloy phase stable and regulates the work-hardening mechanism. Local dynamic-recrystallization behavior and grain evolution are observed in the as-prepared alloy during compression at 800 and 1000°C, which results in the high-temperature softening. This alloy with a muti-phase hierarchical structure would provide a new paradigm for the development of next-generation low-density, high-entropy structural materials for high-temperature applications. [Figure not available: see fulltext.].