Journal of Materials Research and Technology Journal of Materials Research and Technology
J Mater Res Technol 2017;6:390-5 DOI: 10.1016/j.jmrt.2017.07.002
Original Article
Comparisons of self-annealing behaviour of HPT-processed high purity Cu and a Pb–Sn alloy
Yi Huanga,, , Shima Sabbaghianradb, Abdulla I. Almazroueec, Khaled J. Al-Fadhalahd, Saleh N. Alhajeric, Nian Xian Zhanga, Terence G. Langdona
a Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, United Kingdom
b Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, United States of America
c Department of Manufacturing Engineering, College of Technological Studies, P.A.A.E.T., Shuwaikh, Kuwait
d Department of Mechanical Engineering, College of Engineering & Petroleum, Kuwait University, Safat, Kuwait
Received 13 June 2017, Accepted 13 July 2017
Abstract

Early published results have demonstrated that high purity Cu and a Pb–62% Sn alloy exhibit very different behaviour during high-pressure torsion (HPT) processing at room temperature and subsequent room temperature storage. High purity Cu showed strain hardening behaviour with a refined grain structure during HPT processing whereas a Pb–62% Sn alloy displayed a strain weakening behaviour because the hardness values after HPT processing were significantly lower than in the initial as-cast condition even though the grain size was reduced. During room temperature storage after HPT processing, high purity Cu with lower numbers of rotations softened with the time of storage due to local recrystallization and abnormal grain growth whereas the Pb–62% Sn alloy hardened with the time of storage accompanied by grain growth. Through comparisons and analysis, it is shown that the low absolute melting point and the high homologous temperature at room temperature in the Pb–62% Sn alloy contribute to the increase in hardness with coarsening grain size during room temperature storage.

Keywords
High-pressure torsion, High purity Cu, Pb–62%Sn alloy, Self-annealing
J Mater Res Technol 2017;6:390-5 DOI: 10.1016/j.jmrt.2017.07.002