Strengthening of a Pd-free high gold dental alloy for porcelain bonding by a pre-firing heat treatment

Objectives The purpose of the present investigation was to report a Pd-free high gold alloy for porcelain bonding based on the ternary system of Au–Pt–Zn with a nominal composition of 86Au–11Pt–1.5Zn–0.5In–0.7Rh–0.2Fe–0.1Ir (wt.%). Emphasis was put on the effect of a pre-firing heat treatment on the mechanical properties of the alloy. Methods The strengthening effect of the pre-firing heat treatment was investigated by means of hardness measurement, tensile testing, X-ray diffraction, optical microscopy and scanning electron microscopy. Results Experimental results showed that both the hardness and tensile strength of the alloy can be significantly improved after heat treatment at the temperature of 980 °C for 15 min. The strengthening could be attributed to homogenization of microstructure and alloying elements and precipitation of new fine particles. Significance The cast framework of the present new Pd-free alloy could be heat treated before actual firing, and this would improve the processing properties of the alloy during firing.