Structural evolution of non-dendritic AlSi7Mg alloy during reheating
(General Research Institute for Nonferrous Metals, Beijing100088, P.R.China)
Abstract: The structural evolution of non-dendritic AlSi7Mg alloy during reheating in resistance furnace was studied. The alloy ingots were produced by electromagnetic stirring during solidification. It was found that, the Si phase in eutectic dissolves in a way of diffusion towardαphase, its appearance changes from flake to dot-like, and tends to be fine and spheroidal with increasing reheating temperature. The thinner the flake, the lower the temperature for the occurrence of this process, and the higher the transforming speed. The eutectic melts partially when Si phase dissolves to some extent, and the morphology and size of primaryαphase begin to change. The dendrite and rosetteαphases tends to sphericize. The size of the former becomes larger, while the size of the latter reduces to be 1/2~1/4 of the original size. The spheroidal primaryαphase has a tendency of grain growth.
Key words: aluminum alloys; reheating; non-dentritic structure; transformation