Combined volumetric, energetic and microstructural defect analysis of ECAP-processed nickel

TL;DR

This study combines volumetric, energetic, and microstructural analyses to investigate defect annealing in ultrafine grained nickel processed by ECAP, revealing distinct defect types and their kinetics during heating.

Contribution

It introduces a comprehensive method integrating dilatometry, DSC, and microstructural characterization to quantify defect types and their annealing behavior in ECAP-processed nickel.

Findings

Quantified vacancy concentration and dislocation density.

Identified distinct defect relaxation kinetics.

Measured grain boundary expansion and its excess.

Abstract

Difference dilatometry and differential scanning calorimetry (DSC) are used to investigate defect annealing in ultrafine grained nickel processed by equal channel angular pressing (ECAP) at various temperatures. Different defect types and processes such as vacancies, dislocations, grain boundaries and grain-boundary relaxation can be detected. They can be distinguished due to their distinct kinetics as revealed by the release of excess volume and excess heat during linear heating. The data are quantified in combination with a detailed characterization of the microstructure. Values for the absolute vacancy concentration, the dislocation density, the grain boundary expansion and the excess of grain boundary expansion in ECAP-processed nickel are derived.