Alloy material for thixocasting, process for preparing semi-molten alloy material for thixocasting and thixocasting process

摘要

A differential thermal analysis thermograph for a thixocasting aluminum alloy material is such that, a relationship, E1>E2, is established between a peak value E1 of a first angled endothermic section generated by eutectic melting and a peak value E2 of a second angled endothermic section generated by melting of an element having a melting point higher than the eutectic point. Thus, a liquid phase produced by the eutectic melting has a large latent heat due to the fact that the peak value E1 of the first angled endothermic section is larger than the peak value E2 of the second angled endothermic section in a semi-molten eutectic aluminum alloy material derived from the thixocasting aluminum alloy material. As a result, in a solidification step of the thixocasting process, a liquid phase produced by the eutectic melting is sufficiently fed around a solid phase in response to the solidification and shrinkage of the solid phase, and then solidified. Thus, it is possible to produce a casting free from defects such as voids on the order of a micron.