Effect of Mn content on the microstructure of Al-Mn alloys electrodeposited at 150°C

Al-Mn alloys with compositions ranging between 0-50 wt% Mn were electrodeposited at 150°C onto copper substrates from a chloroaluminate molten salt electrolyte with controlled additions of MnCl2. The results of examination by SEM, TEM, EDAX and x-ray diffraction are presented. The formation of amorphous phases occurs in a relatively narrow compositional range compared to that which corresponds to the formation of the crystalline phases. For lower and higher Mn contents, the competition of surface diffusion and joining of adatoms causes the formation of metastable phases as well; these phases, however, have a crystalline structure.