On the evolving nature of c/a ratio in a hexagonal close-packed epsilon martensite phase in transformative high entropy alloys.

摘要: Activation of different slip systems in hexagonal close packed (h.c.p.) metals depends primarily on the c/a ratio, which is an intrinsic property that can be altered through alloying addition. In conventional h.c.p. alloys where there no diffusion-less phase transformation and associated volume change with deformation, ratio remains constant during deformation. present study, epsilon martensite transformative high entropy (HEAs) were quantified as functions alloy chemistry, friction stir processing tensile The study revealed while dependent elements, HEAs changes This attributed to induced dependence lattice parameters microstructure stress state. Lower than ideal promotes non-basal pyramidal 〈c + a〉 deformation twinning HEAs. Also, a unique twin-bridging mechanism was observed, provided experimental evidence supporting existing theoretical predictions; i.e., geometrical factors combined grain orientation, plastic result characteristic twin boundary inclination at 45–50°.