Reversible deformation-induced martensitic transformation in Al_0.6CoCrFeNi high-entropy alloy investigated by in situ synchrotron-based high-energy X-ray diffraction

The micro-mechanical behavior of Al_0.6CoCrFeNi high-entropy alloy during tensile deformation was investigated using an in situ synchrotron-based high-energy X-ray diffraction technique. The alloy consisted of face-center-cubic (FCC) and body-center-cubic-based (BCC-based) structure accompanied by a small amount of σ phase. The FCC phase yielded prior to the BCC-based phase during the tensile loading, and the BCC-based phase bore more stress partition during the plastic deformation stage in spite of only ∼23% volume fraction. A reversible deformation-induced martensitic transformation from the BCC-based phase to orthorhombic phase was observed during the plastic deformation stage. The transformation preferentially occurred in the grains with an orientation of B-[001]//loading direction and B-[110]//transverse direction. The study characterized the micro-mechanical behavior of this alloy, and the reversible martensitic transformation is believed to be beneficial to the fracture toughness of such alloys.