Near-Equiatomic µ Phase in Self-Sharpening Tungsten-Based High-Entropy Alloys

Abstract

The topologically close-packed (TCP) µ phase is usually known as an undesirable precipitation in highly alloyed Ni-base superalloys and steels. However, the ultrastrong µ phase with micron/nano-scale distribution plays a key role in driving the emergence of self-sharpening in our recently developed WMoFeNi high-entropy alloy (HEA). Herein, a detailed study is carried out to understand the substructure and atomic occupation of the µ phase by scanning electron microscope (SEM) and aberration-corrected transmission electron microscope (ACTEM). The Fe/Ni and W/Mo element pairs are equivalent in the µ-phase structure. Moreover, the elements in µ phase exhibit a near-equiatomic ratio, and the µ phase can grow during annealing at 1150◦ C. (0001)µ and (1102)µ. Twins are the main substructures of the µ phase, and their atomic configurations and twinning mechanisms are investigated. The geometrical structural analysis of µ phase possesses a great significance for the design of self-sharpening HEAs.