Effect of ball milling on microstructural evolution during partial remelting of 6061 aluminum alloy prepared by cold-pressing of alloy powders

The effect of ball milling on the microstructural evolution was investigated during partial remelting of 6061 aluminum alloy prepared by cold-pressing of atomized alloy powders. The results indicate that the microstructural evolution of 6061 aluminum alloy can be divided into three stages, the dissolution of eutectic phases and the coarsening and growth behavior of the resulting grains, structural separation and spheroidization of primary particles, and the final coarsening behavior of the particles. Compared with the alloy without ball milling, ball milling accelerates the first stage of microstructural evolution due to the energy stored in the powders, but the latter two stages are slowed down because of the formation of large-sized powders. Moreover, the finer the as-cold-pressed microstructure is, the smaller and more spherical the primary particles in the final semisolid microstructure are. Furthermore, properly elevating the heating temperature is beneficial for obtaining small and spheroidal particles.