Influence of Heavily Rolled Heterogeneous Nano–Structure on Strength of Cu–Be–Co Alloys

Abstract

Heterogeneous–nano （HN） structures induced by heavy cold rolling of Cu–Be–Co alloys and their influence on the mechanical properties were systematically investigated to develop thermo–mechanical process applicable to the industrial mass–production. The HN–structure was successfully developed by the combination of differential speed cold rolling and simple cold rolling with the reduction up to 97％ at maximum after the solution–annealing between 850 and 867°C. The HN structure possessed characteristic eye–shaped domains consisting of alternatively stacked deformation twin bands. Aging at 285°C of the HN structured Cu–1.86mass％Be–0.23mass％Co alloy caused a marvelous tensile strength of 1.78 GPa, which was significantly higher than that of 1.3 GPa of a conventional Cu–Be–Co alloy （C17200） fabricated by conventional thermo–mechanical processes. It was also shown that the developed HN structured Cu–Be–Co alloy exhibited comparable bending formability and electrical conductivity with those of the conventional one. While, in contrast, the fatigue strength was slightly lower than that of the conventional one. It is confirmed that introduction of HN structured Cu–Be–Co alloys can be fabricated by means of a newly developed thermo–mechanical process applicable to the industrial–scale mass production.