Abstract
The cast 53Ag-30Pd-17Cu(AP), 53Ag-30Pd-17Cu-5Zn(APZ), and 70Au-10Ag-3Pd-3Pt-14Cu(Type IV)alloys were solution-treated at 700, 750, 800℃ for 3, 33, 63, 93min, softened by water quenching(Q), and then over cooled from 450 to 250℃(H).The change in their Vickers hardness(Hv)under conditions Q and H were examined.In both AP and APZ alloys, Hv after Q increased with the increase in solution treatment temperature and decrease in solution treatment time, however, Hv fluctuation due to solution treatment condition in AP and APZ alloys was ±13 and ±7, respectively, which are small values compared with those in AP and APZ subjected to H.The Hv of hardened AP and APZ increased as the solution treatment temperature increased in both AP and APZ, reaching 327 and 279 for AP and APZ, respectively, after solution treatment at 800℃ for 33min.When hardened, APZ which contains Zn had an Hv smaller than that of AP which contains no Zn, and a zinc-soluted PdCu order lattice phase was already observed after quenching.In the Type IV alloy, the changes in the solution treatment temperature and time did not give rise to the changes in Hv after Q or H.The changes in Hv after Q and H were explained based on phase transformation.
