Effects of Native AlN Particles on Heterogeneous Nucleation in an Al-3Fe Alloy

The naturally formed inclusions in an Al-3Fe alloy were investigated using a pressurized melt filtration technique. Naturally formed AlN particles with a rodlike morphology and a size distribution between 200 nm and 4 µm coexist with the native Al2O3 particles in the Al-3Fe alloy. These native AlN particles were investigated with scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). A well-defined orientation relationship (OR) between AlN and α-Al was found from the AlN particle embedded in α-Al. A tilt angle of 5.8 deg was observed between {111}α-Al and {0001}AlN at the α-Al/AlN interface. The atomic matching for the α-Al/AlN interface was investigated by considering interfacial segregation on the AlN particles. The heterogeneous nucleation potency of the native AlN particles was investigated. Although these native AlN particles can nucleate the α-Al, the contribution is very small. This contribution reveals the heterogeneous nucleation of α-Al on the native AlN particles and the competitive relationship between the native Al2O3 and AlN as the nucleation substrates. The surface modification of the native AlN in Al alloys containing multiple alloy elements and the corresponding effects on the heterogeneous nucleation were preliminarily investigated.