Solidification process and microstructure of transition layer of Cu-Al composite cast prepared by method of pouring molten aluminum

The Cu-Al composite casts were prepared by the method of pouring molten aluminum. The solidification process and the microstructure of the transition layer were investigated during the recombination process of the liquid Al and the solid Cu. The results reveal that the microstructure of the transition layer in the Cu-Al composite cast consists of a(Al)+alpha(Al)-CuAl2 eutectic, alpha(Al)-CuAl2 eutectic, CuAl2+alpha(Al)-CuAl2 eutectic and Cu9Al4. Additionally, the pouring temperature, cooling mode of the Cu plate surface and start time of the forced cooling after pouring have no effect on the microstructure species. But the proportion of the various microstructures in the transition layer changes with the process parameters. The pure Al at the top of the transition layer starts to solidify first and then the a(Al) phase grows in a dendritic way, while the CuAl2 phase exhibits plane or cellular crystal growth from the two sides of the transition layer towards its interior. The stronger the cooling intensity of the Cu plate outer surface, the more developed the dendrite, and the easier it is for the CuAl2 phase to grow into a plane crystal.