Strength changes during heat treatment of HPT-processed Copper and Nickel

Author(s)
Peter Cengeri, Michael B. Kerber, Erhard Schafler, Michael J. Zehetbauer, Dania Setman
Abstract

This work investigated the changes of strength during isochronal heating of Cu and Ni after HPT (high pressure torsion) processing. By means of Vickers microhardness, not only decreases but even increases of strength were observed, and the concomitant changes of microstructure have been monitored by means of in-situ Synchrotron X-ray Bragg profile analysis (SXPA). The latter informed on changes of the crystallite size as well as of the dislocation density. A comparison with literature and the authors' previous measurements suggest that the strength increases to arise from the agglomeration and annihilation of vacancies, at homologous temperatures between T = 0.25 - 0.3T(m) corresponding to classical annealing stages III and IV. According to the SXPA data, the significant decrease of strength at homologous temperatures between T = 0.3 - 0.4T(m) is accompanied by both a drastic increase of crystallite size as well as by massive annealing of dislocations being part of the HPT-induced crystallite boundaries. As these features are typical of primary recrystallisation, this stage is identified as annealing stage V. The dependences of the stages' typical temperatures on the strain and hydrostatic pressure of HPT treatment confirm the interpretation of stages in terms of the specific annealing defects.

Organisation(s)
Physics of Nanostructured Materials
Journal
Materials Science and Engineering A: Structural Materials: Properties, Microstructures and Processing
Volume
742
Pages
124-131
No. of pages
8
ISSN
0921-5093
DOI
https://doi.org/10.1016/j.msea.2018.11.010
Publication date
01-2019
Peer reviewed
Yes
Austrian Fields of Science 2012
Material sciences, Materials physics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/strength-changes-during-heat-treatment-of-hptprocessed-copper-and-nickel(7f2a739f-fdc5-45a2-8fbc-9d52f78359bb).html