Significant lattice-distortion effect on compressive deformation in Mo-added CoCrFeNi-based high-entropy alloys

Large lattice distortion is an essential feature of high-entropy alloys (HEAs). Herein, the deformation behaviors of three types of as-cast CoCrFeNi-based HEAs, which contained 0, 7.9, and 17.1 wt% Mo, were comparatively studied through compressive tests and microstructural observations. The intrinsic lattice distortion increased mainly as a function of the Mo content. By virtue of both the local strain incompatibility inside the coarse columnar grains of the as-cast microstructures and low dislocation mobility in HEAs, domain rotations were induced at low strains. Meanwhile, simple shear occurred between domains and produced a new boundary network in the microstructure. The large lattice distortion of the high-Mo HEA (17.1 wt%) gave rise to intense planar slip bands, on which a large number of dislocations slipped and impinged on strain-induced boundaries. As a result of the high back-stress hardening, the high-Mo HEA exhibited enhanced strain-hardening. At high strains, the stress concentration events increased as the lattice distortion of the HEAs increased; this promoted twin growth in the high-Mo HEA. The high-Mo HEA was highlighted with a high strain-hardening rate over a wide strain range. In this study, high-strength as-cast HEAs were developed based on the utilization of the latticedistortion effect.

Automated summary

The study compared the deformation behaviors of different Mo content HEAs and found that lattice distortion is a key factor affecting the deformation behavior of HEAs, with high-Mo HEAs exhibiting a higher strain-hardening rate.