Abstract: The effects of thermal history of liquid metal Al on its solidification microstructures have been studied by using molecular dynamics simulation. It has been found that under different thermal history conditions, in the same system, both the 1551 bond-type and the icosahedron (expressed by (12 0 12 0)) related to the 1551 bond-type play a remarkable role during microstructure transitions (see Fig.4). The number of repeatable icosahedra not always increased with the decrease of temperature and has a maximum during the isothermal runs at given temperatures (see Fig.6). The maximum point corresponds to the glass transition temperature Tg, and can be moved under different thermal history conditions. It is also demonstrated that the thermal history conditions seriously influence the solidification microstructures and their effects are mainly demonstrated after the glass transition point. These results give a new way to understand and control the microstructure transitions during solidification processes.

Key words: Liquid metal, Rapid solidification, Thermal history condition, 　Microstructures, Computer simulation