Microstructure and mechanical properties of Cu-Ni-Si alloys

The microstructure and mechanical properties of 0.1 wt.% Mg-added and Mg-free Cu-2.0 wt.% Ni-0.5 wt.% Si alloys aged at 400 degrees C have been examined. The addition of Mg promotes the formation of disk-shaped Ni(2)Si precipitates. The Cu-Ni-Si-Mg alloy exhibits higher strength and resistance to stress relaxation than the Cu-Ni-Si alloy. The higher strength or stress relaxation resistance is attributable to the reduction in inter-precipitate spacing by the Mg addition or the drag effect of Mg atoms on dislocation motion. The Cu-Ni-Si alloy with a large grain size of 150 mu m shows higher stress relaxation resistance than the alloy with a small grain size of 10 mu m because of a lower density of mobile dislocations in the former alloy. (c) 2007 Elsevier B.V. All rights reserved.