Mold Surface Roughness Effects On The Microstructure And The Hot Tearing Strength For An Al-4.5 percent Wt Cu Alloy

摘要

The effects of D.C. casting mold roughness on the microstructure and the strength to hog tearing was investigated for an Al-4.5 percent wt percent Cu alloy. Mold surface roughness has been found to influence the resulting grain size near the surface by the preferential nucleating and growth on surface asperities. This grain size variation was found to influence the mechanical response of the semi-solid material which can be associated to the hot tearing susceptibility. The effect of the mold roughness on the resulting microstructure was also reproduced using a simple cellular automaton model. A "surface efficiency coefficient" is proposed to characterize the cyclic effect of the mold surface roughness on the resulting grain size. This coefficient if defined to represent the combined effects of the localized casting shrinkage and the liquid/mold contact distribution.