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

The topologically close-packed (TCP) mu phase is usually known as an undesirable precipitation in highly alloyed Ni-base superalloys and steels. However, the ultrastrong mu 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 mu 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 mu phase structure. Moreover, the elements in mu. phase exhibit a near-equiatomic ratio, and the mu phase can grow during annealing at 1150 degrees C. (0001)(mu) and (1 (1) over bar 02)(mu) twins are the main substructures of the mu phase, and their atomic configurations and twinning mechanisms are investigated. The geometrical structural analysis of mu phase possesses a great significance for the design of self-sharpening HEAs.

Automated summary

The topologically close-packed (TCP) mu phase is typically considered as an undesirable precipitation in highly alloyed Ni-base superalloys and steels. However, in our recently developed WMoFeNi high-entropy alloy (HEA), the ultrastrong mu phase with micron/nano-scale distribution plays a crucial role in driving the emergence of self-sharpening. Through the use of scanning electron microscope (SEM) and aberration-corrected transmission electron microscope (ACTEM), a detailed study was conducted to understand the substructure and atomic occupation of the mu phase. The results reveal that the Fe/Ni and W/Mo element pairs are equivalent in the mu phase, and the elements exhibit a near-equiatomic ratio. Additionally, the mu phase can grow during annealing at 1150 degrees C, and the main substructures of the mu phase are (0001)(mu) and (1 (1) over bar 02)(mu) twins, whose atomic configurations and twinning mechanisms were investigated. The geometrical structural analysis of the mu phase is significantly important for the design of self-sharpening HEAs.