Microstructural investigation of plastically deformed Ti20Zr20Hf20Nb20Ta20 high entropy alloy by X-ray diffraction and transmission electron microscopy

Abstract

The microstructure evolution in body-centered cubic (bcc) Ti20Zr20Hf20Nb20Ta20 high entropy alloy during quasi-static compression test was studied by X-ray line profile analysis (XLPA) and transmission electron microscopy (TEM). The average lattice constant and other important parameters of the microstructure such as the mean crystallite size, the dislocation density and the edge/screw character of dislocations were determined by XLPA. The elastic anisotropy factor required for XLPA procedure was determined by nanoindentation. XLPA shows that the crystallite size decreased while the dislocation density increased with strain during compression, and their values reached about 39nm and 15×1014m−2, respectively, at a plastic strain of ~20%. It was revealed that with increasing strain the dislocation character became more screw. This can be explained by the reduced mobility of screw dislocations compared to edge dislocations in bcc structures. These observations are in line with TEM investigations. The development of dislocation density during compression was related to the yield strength evolution.