Abstract
The surface appearance, microscopic roughness of wrinkles, and solidification patterns of experimental castings made by a directional solidification method using a chill and high temperature molds were examined. In the cases of pure Sn, pure Pb, and Sn-Pb alloys, one or two wrinkles were observed on the surface of the castings made by the method. The wrinkles were always located in the vicinity of the contacted chill edge, implying a correlation between the wrinkles and cooling by the chill. By measuring the difference in height of the wrinkles, it was found that there is positive correlation between the difference in the height and Nd which is a parameter which shows the thermal deformation amount of the solidified shell defined by S. Dong et al. From the cross-sectional shapes of poured-out pure Sn castings and cross-sectional macro structure of Zn-2%Al casting, it was found that the solidified shell forms near the chill position, and that the solidification direction changes in the vicinity of the chill edge, indicating that displacement by deformation of the solidified shell can become concentrated in the vicinity of the chill edge. These results suggest that wrinkle formation is caused by the thermal deformation of the solidified shell formed by the contacted chill.
