Abstract
Cu-Zr aged alloys are very interesting as high strength and high electrical conductivity alloys. The precipitation and electrical conductivity change during aging of Cu-Zr binary and Cu-Zr-Si ternary alloys were investigated by means of hardness and electrical resistance measurements and structure observations.
Decomposition of the Cu-Zr super-saturated solid solution during aging occurs by forming a plate-like stable phase with cubic crystal structure. The plate-like precipitates are preferentially precipitate in the grain boundary and so the precipitate free zones about 1 μm in width are formed.
The addition of 0.1∼0.3 mass%Si eliminated the precipitate free zone near the grain boundary and the Cu-Zr-Si ternary fine precipitate within a grain are coarsened slowly during high temperature holding. Thus, the addition of Si to the Cu-Zr binary alloy contributes simultaneously to the retardation of decreasing hardness at high temperature and the improvement of heat resistance.
