Improvement in Strength of High Concentration Corson Alloy with the Heterogeneous-Nano Structure

Abstract

Effects of pre-aging of Corson alloys with high concentrations of Ni and Si (Cu–4.2 mass%Ni–0.93 mass%Si) followed by heavy cold rolling and full-aging on strengthening were systematically investigated. Especially, development of heterogeneous-nano (HN) microstructure was focused. And the relationship of mechanical/electrical properties was precisely examined. The pre-aged alloys exhibited a considerable strengthening after 90% cold rolling. This was attributed to the increase in the volume fraction of deformation twin domains in the HN microstructure after cold rolling as well as the precipitation strengthening. The sample prepared by a thermo-mechanical process via pre-aging at 723 K, subsequent cold rolling and full-aging at 673 K for 600 s exhibited the best strength/conductivity balance with an ultimate tensile strength (UTS) of 1096 MPa and electrical conductivity (E) of 29% IACS. When examined the effects of solid-solution (SS) temperature on the microstructure and properties, SS at 1223 K derived finer grain size than at 1323 K and the achieved best balance of UTS and E with 1061 MPa and 33% IACS. Therefore, grain refinement prior to pre-aging had no significant effect on strengthening but contributed to modification of electrical conductivity.