Abstract:The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg₇Zn₃ alloys were investigated by molecular dynamics simulation. The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10¹² K/s, and the 1551 bond-type and the icosahedron basic cluster (12 0 12 0 ) played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature T_g; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.

Key words: liquid Mg-Zn alloy; initial melt temperature; microstructure evolution; molecular dynamics simulation; cluster-type index method