Development of 12%Au-20%Pd-Ag casting dental alloy

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It is aimed in this study to create a new dental alloy, which copper content is raised up to the eutectic zone, strength is increased greatly and toughness is not lower than that of gold alloys. It had been shown by the relative results that inhibiting the volume rate of the β phase can block the degradation of the fatigue property. To acquire further understanding to the alloy for next-step efforts, the work of the present year, the continuance of the last-year operations, was to conduct fatigue tests of casting 12%Au-20%Pd-Ag alloy in ambient atmosphere, and to look into the mechanism of fatigue fracture from the angle of the relation between casting defects and fatigue strength.1. The casting products of the alloy show apparently lower fatigue strength than that of the working products by air-cooling at 1073K both in low and high cycle regions. The casting of water cooling at 1123K, however, among all the casting cooling plans, brings the highest fatigue strength for the relevant casting product in the high cycle region, indicating the fact that the fatigue-resistant property of the alloy is not prone to be affected by volume shrinkage accompanying in the casting process.2. In the zone of high loads combining low cycles the higher volume shrinkage rate is the lower the fatigue strength of the casting products is, but in the zone of low loads combining high cycles the effect of shrinkage is so limited that one can almost neglect the influence of shrinkage on the growth of fatigue cracks.The above facts indicate that diminishing the effect of casting defects on the fatigue strength and increasing the fatigue strength are available by solution treating the casting materials at 1123K.