dislocation-type evolution in quasi-statically compressed polycrystalline nickel
Name: Chaoyi Zhu
Grad Year: 2022
Study of evolution of different types of dislocations, either GND or SSD, has long been a challenge due to the lack of reliable large-scale quantitative experimental technique. With EBSD-based GND calculation, the nature of dislocation generation as a function of applied plastic strain (0.05 to 0.46) in quasi-statically compressed polycrystalline pure nickel has been studied experimentally at ambient temperature. More specifically, the geometrically-necessary dislocation densities associated with non-uniform plastic deformation measured over large (several millimeter square) areas were computed using Hough-based EBSD methods. In addition, the total dislocation density responsible for the overall work hardening is estimated from the measured flow stress based on Taylor's hardening model. Next, the statistically stored dislocation (SSD) density is calculated by subtracting the GND density from the total dislocation density. It enables the interplay of GNDs and SSDs in the hardening of nickel to be gleaned in a quantitative sense. This study illustrates that GNDs are the more important hardening factor in the early stages of deformation of polycrystalline metals, whereas SSDs dominate the hardening process at larger strains, comparable with the early predication made by Ashby (1970).
Industry Application Area(s)
Aerospace, Defense, Security | Civil/Structural Engineering | Materials