High strength copper alloys by thermomechanical treatments

Abstract

A thermomechanical processing technique for in creasing the strength of copper alloys is described. Alloys studied include phosphor bronze (5 pct Sn), nickel silver (12 pct Ni-28 pct Zn), tin-modified cupronickel (9 pct Ni-2 pctSn), and Cu−Be (2 pct Be). In this technique, the material is cold-rolled to about 95 pct reduction in thickness followed by heat treatment below the recrystallization temperature. The severe cold work results in increased strenght through strain hardening and texture strengthening, but at the expense of decreased ductility. The terminal heat treatment recovers the ductility while maintaining or increasing the strength imparted by cold work alone. Preliminary results indicate that cold work-accelerated precipitation is chiefly responsible for the strength increase during heat treatment. As a result of the present processing, the copper alloys exhibit higher yield strengths for given amounts of ductility than have heretofore been attained.