Dynamic Shear Deformation of a CrCoNi Medium-Entropy Alloy with Heterogeneous Grain Structures

Abstract

Single-phase CrCoNi medium-entropy alloys (MEA) are emerging recently as an interesting class of metallic materials, but the dynamic response of this MEA at high strain rates remains unknown. High-entropy alloys (HEA) and MEA, containing multiple elements typically with equal molar fraction, have emerged recently as an interesting class of materials. This class of alloys can be solid solutions with a simple crystal structure, such as fcc, and the random distribution of multiple elements can reduce energy penalty for the formation of stacking fault, rendering low stacking fault energy. The equimolar CrCoNi MEA was produced via electromagnetic levitation melting in a high-purity argon atmosphere, and cast to ingots with a diameter of 120 mm and a height of 100 mm. Scanning electron microscope, electron backscattered diffraction, transmission electron microscope and high resolution electron microscope have been used to characterize the microstructures before and after dynamic shear testing.