Microstructure and Mechanical Properties of Cu-Ni-Si Alloys
Chihiro WATANABE, Hiroaki HIRAIDE, Zuogui ZHANG and Ryoichi MONZEN
Abstract:The microstructure and mechanical properties of thermo-mechanically treated Cu-2.0mass%Ni-0.5mass%Si alloys with and without 0.1mass%Mg have been investigated. The Mg addition increases the formation rate of disk-shaped Ni2Si particles. The Mg addition produces higher strength and resistance to stress relaxation. The improvement of strength or stress relaxation resistance is caused by the decrease in interparticle spacing by the Mg addition or by the Mg-atom-drag effect on dislocation motion. The stress relaxation resistance for the Cu-Ni-Si alloy with a large grain size of 150mm is higher than that for the alloy with a small grain size of 10mm because the density of mobile dislocations in the former alloy is lower. The effect of equal channel angular pressing (ECAP) and subsequent heat treatment on the mechanical properties of the Cu-Ni-Si alloy has also been studied. The heat-treated ECAP alloy shows larger values of 0.2 % proof stress and ultimate tensile stress and a slightly smaller value of elongation to failure compared with the thermo-mechanically treated Cu-Ni-Si alloy. Key Words:Copper-Nickel-Silicon alloy, Age hardening, Ni2Si precipitates, Stress relaxation, Equal channel angular pressing