High Strength Ag-Pd-Cu Alloys

Twelve kinds of Ag-Pd-Cu alloy, containing 25, 30, 35, 40wt% Pd, 20, 25, 30wt% Cu and the residual quantity 30〜55wt% Ag were melted in an argon atmosphere.These alloys were cast using dental precision casting, subsequently, softening heat treatment(water quenching from 800℃)and hardening heat treatment(450→250℃ 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 60kgf/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 in the range of 73〜107kgf/mm2.However, elongation decreased to 0.5〜3.5%.Composition of the alloy that had the maximum tensile strength(104kgf/mm2)was about 45Ag-35Pd-20Cu.Brightness(L*)of the test pieces that were immersed in 0.1% sodium sulfide solution of 37℃ 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.