Topic: Microstructure, texture and strength evolution during severe plastic deformation of CrMnFeCoNi high-entropy alloy

Speaker: Prof. W. Skrotzki

　　　　　Institut für Festkrper- und Materialphysik, Technische Universitt Dresden, Germany

Time: 10:00-11:30, July 22 (Monday), 2019

Venue: Room 468, Lee Hsun Building

Welcome to attend!

Abstract：

An equiatomic high-entropy alloy CrMnFeCoNi has been severely deformed by high pressure torsion at room and liquid nitrogen temperature (RT and LNT). The microstructure and texture has been analyzed by X-ray diffraction (X-ray line profile analysis and X-ray microdiffraction, respectively). It is shown that at a certain shear strain a steady state domain/grain size in the nanometer range and a dislocation density of the order of 1016 m-2 is reached, while the twin density at RT goes over a maximum at this strain. At LNT above a certain hydrostatic pressure HPT deformation is accompanied by phase transformation from face-centred cubic (fcc) to hexagonal (hcp). The amount of hcp phase increases with increasing pressure. The texture developed is typical for sheared fcc metals with a weak brass-type shear component dominating. Moreover, microhardness tests have been applied. Analysis of the strength suggests a Taylor-type hardening. The results will be discussed with regard to the mechanisms of deformation, including dislocation slip, twinning, martensitic transformation and grain boundary sliding.