Optimisation of Post-Densification Cold Rolling Schedule for PM Copper Strip

Abstract

Preparation of fully dense copper strip from Cu₂O powder via an integrated powder technology route is briefly described. Full density strip obtained by such a route has been found to contain 0·5 vol.-% of Cu₂O inclusions, a somewhat higher level than that found in strip prepared from atomised copper powder. Internal degradation of full density PM copper strip by inclusion-matrix decohesion and/or inclusion fragmentation during cold rolling has been studied as a function of thickness reduction. Coarse inclusions ≥10 μm in size undergo fragmentation/decohesion at relatively small thickness reductions of the order of 20%.In contrast, smaller inclusions in the submicrometre range do not exhibit decohesion/fragmentation after thickness reductions of as high as 60%. Cold rolling thickness reductions up to 20 and 40% were found to be safe for strip prepared from Cu₂O and atomised copper powders respectively. For strip produced from Cu₂O powder and cold rolled to 20% thickness reduction an annealing treatment at 823 K for 1800 s was found to give optimum properties. Finished strip thus produced had a tensile strength of 228 ± 2 MN m⁻², elongation to failure of 46 ± 1%, and an electrical conductivity of 99·0 ± 0·18%IACS. PM/0651