Consturuction of Analysis System for Deformation Behavior during Solidification of Metallic Materials

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For metals processings which aim at higher quality and higher productivity, solidification crack is one of the worst obstruction variables to overcome. Therefore we investigated the deformation behavior of carbon steels and copper-tin alloys during and after solidification. We carried out high temperature tensile tests for samples which have higher carbon contents to 0.8wt% and for samples which have higher sulfur contents. We also investigated the influence of strain rate on mechanical properties during solidification of 0.6wt%C samples. As a result of the high temperature tensile test, ZST(Zero Strength Temperature) was determined to be the temperature which corresponds to the solid fraction of about 0.7 for both high carbon samples and high sulfur samples as is same with the previous experimental results. On the contrary little ductility was observed even below the temperature at which solidification completes according to the numerical analysis, and ZDT could not be determined. The reason why ZDT does not correspond to the solid fraction of 1 seems to be the low purity of the samples compared with the previously tested samples. For example, having both sulfur and phosphorus are more contained for about. However the mechanism of causing the ZDT drop remains unexplained. The increase of strain rate gave rise of the tensile strength, and around 5mm displacement was measured under strain rate of 10^<-3>/s though little displacement was observed under strain rate of 10^0-10^<-2>/s. Consequently it is concluded that the mechanical properities depend on the strain rate even in the solidification temperature range.As for copper-tin alloys deformation behavior under strain tate of 10^0-10^<-4>/s was measured at the temperature range below the solidus. Regression equations for tensile strength, flow stress and elongation are obtained in relation to testing temperature, strain rate and/or strain.