Heterogeneous nucleation of α-Al on naturally formed MgAl2O4 particles during solidification of Al-Mg-Si-Fe-Mn alloys

The nature of the native MgAl2O4 particles found in an Al-5Mg-2Si-0.7Mn-1.1Fe alloy was investigated with scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). An orientation relationship (OR) was identified to be: 8.5 degrees(-1 1 -1)[-1 1 0]alpha-Al//(2 -2 2)[-1 1 0]MgAl2O4. Different from the OR between the alpha-Al and the MgAl2O4 particles with a "clean" surface [1], a tilt angle (8.5 degrees) was observed. The atomic templating layer during the nucleation process of alpha-Al on MgAl2O4 was investigated by considering the interfacial segregation. The contribution of native MgAl2O4 particles to the grain refinement was investigated.