High strength Ag-Pd-Cu alloys

Abstract

Twelve kinds of Ag-Pd-Cu alloy, containing 25, 30, 35, 40 wt% Pd, 20, 25, 30 wt% Cu and the residual quantity 30-55 wt% Ag were melted in an argon atmosphere. These alloys were cast using dental precision casting, subsequently, softening heat treatment (water quenching from 800 degrees C) and hardening heat treatment (450-250 degrees C oven cooling) were applied. After softening heat treatment, the Vickers hardness, tensile strength, and elongation of the experimental alloys ranged from 145 to 200, from 41 to 60 kgf/mm2 and from 11 to 27%, respectively. Therefore, these alloys were very ductile in softening heat treatment condition. After hardening heat treatment, the Vickers hardness of the alloys increased in the range of 241-433 and tensile strength increased in the range of 73-107 kgf/mm2. However, elongation decreased to 0.5-3.5%. Composition of the alloy that had the maximum tensile strength (104 kgf/mm2) was about 45 Ag-35 Pd-20 Cu. Brightness (L*) of the test pieces that were immersed in 0.1% sodium sulfide solution of 37 degrees C for 3 days ranged from 58 to 67. After hardening heat treatment, the Ag-Pd-Cu ternary alloy containing 20-30% Cu, 30-40% Pd had satisfactory high hardness and strength for adhesion bridge, but their elongation and tarnishing resistance were insufficient for clinical application.