[Density-temperature change on Ag-Cu binary alloys].

Abstract

In order to investigate the density variance of casting dental alloys according to the change of temperature, a density measurement apparatus based on the sessile drop method was developed. This apparatus consisted of three parts: a furnace, a photo taking system and an image analyzing system. Five Ag-Cu binary alloys: Ag-3%Cu, Ag-15%Cu, Ag-28%Cu, Ag-70%Cu, Ag-97%Cu; were measured from room temperature to 1400 degrees C, and five graphs of Temperature-Density were drawn. From these graphs, densities, at room temperature, solidus point and liquidus point were obtained. Using this data, the solidifying shrinkage and the shrinkage in the solidus phase were calculated. The closer the composition of an alloy to pure metal the higher the solidifying shrinkage, and at the eutectic point the solidifying shrinkage showed the lowest value. It was observed that the metal texture influenced the value of solidifying shrinkage. There were no significant differences of thermal shrinkage in solidus between the five alloys, and each showed approximately 5vol% shrinkage. These values on high thermal condition are considered to be very important as fundamental data necessary for the manipulation of dental casting.