Mechanical, thermal, and chemical analyses of the binary system Au-Ti in the development of a dental alloy.

Abstract

Investigations in the binary system gold-titanium (Au-Ti) were performed in regard to the development of a universal dental alloy suited for inlays, for the conventional crown and bridge technique, as well as for the ceramic-fused-to-metal technique. With nine alloys with increasing Ti content from 0-10 atom %, microstructure, mechanical properties, thermal properties, and corrosion were determined in the as-cast state and after simulation of ceramic firing. The microstructure shows an increasing formation of a second phase with increasing Ti content, crystallizing dendritically, which, according to the binary phase diagram must be the intermetallic phase TiAu(4). The results of the measurements reveal that with increasing Ti content, hardness, Young's modulus, proof stress, and tensile strength strongly increase in the range of 2-6 atom % Ti and with higher Ti content remain constant. Elongation after fracture decreases with a Ti content above 2 atom %. The coefficient of thermal expansion decreases linearly with increasing Ti content. Thermal distortion decreases exponentially with increasing Ti content. The corrosion test showed an increasing release of Ti with increasing Ti content. Lowest corrosion was observed in the simulated state with intact oxide layer. Appropriate properties for dental application were found in the range of 6.5 at% Ti.