Chiesa F, Regimbal P

Abstract: A lost wax cluster of aluminum A356 casting has been the object of a solidification modeling case study. Wide differences in mechanical properties were observed in the T6 heat treated plates, depending on the location of the tensile test sample. Solidification modeling helped explain that these differences resulted from different local solidification times and temperature gradients at the various locations. An attempt at more clearly defining microporosity and macroshrinkage has been made. The different causes of the two defects are outlined. The consequences on the prediction of the two phenomena via solidification modeling are explained. Microporosity is influenced by local solidification time, thermal gradient and by the gas content of the melt. Macroshrinkage depends on the critical fraction solid of the alloy; it only occurs when a “hot spot” exists inside the casting. Predicted microporosity distributions for different gas content of the melt were analyzed. Concurrently, the predicted macroshrinkage was determined; it was shown to exhibit a distribution which is very different from that of microporosity.

Keywords: A356 castings, Distinguishing, Macroshrinkage, Microporosity, Modeling, Solidification