Solidification shrinkage and high temperature characteristics of dental alloy for metal-ceramic.

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High temperature properties of the high noble alloy (KIK-HII) noble alloy (Degubond-J2) were investigated. The thermal expansion percentage and coefficient, and high temperature strengths were investigated up to the liquidus temperature. Furthermore, microstructural and compositiona 1 changes in the solid/liquid dual phase were studied.As the result of examining the microphotograph, at the time of the melting of KIK-HII, it was found out that the many star-like crystals had convected in the liquid phase. In J2, the star-like crystal was growing from the tip of the solid with which the liquid permeated and swelled up. These phenomena had the unknown reason for generation. Then, the silver-palladium-copper-gold alloy (S12) and the gold alloy (Type3) were added, and microstructural changes in the solid/liquid dual phase were studied.Consequently, except the gold-and-silver palladium alloy, the detailed crystal appeared at the time of the melting. However, at the water quenched from liquid … More us point +50℃, the star-like crystal disappeared and the big dendritic crystal appeared from the super-cooled state. Moreover, the star-like crystal did not appear at the any time of solidification.The above examinations, the following conclusions were obtained.1.The solidus point of the KIK-HII was 1209.3±3.2℃, and the liquidus point was 1308.3±7.1℃. The thermal expansion percentage of the melt was 041±0.16%.2.The solidus point of the J2 was 1198.3±0.6℃, and the liquidus point was 1253.0±4.4℃. The thermal expansion percentage of the melt was 4.50±0.80%.3.The high temperature properties were quite different between KIK-HII and J2.4.In the first stage of melting of the dental alloys, small star-like crystals arise, and in the next stage, these crystals disappear by melting into the liquid. With time, other solid parts absorb a liquid ingredient and get fat. The microstructure near liquidus temperature has decisive influence on a solid microstructure.5.The generation and the disappearance of the star-like crystals are considered to do influenc e strong against the optimal casting temperature of the dental alloy. Less