TEM Investigation of Metal/Ceramic Interfaces in AA7475/AlN or Al₂O₃ Nano-Composites

Abstract

Microstructure of two types of 7475 aluminum alloy matrix composites with additions of 10 wt.% and 20 wt.% of Al2O3 or AlN were investigated. Pre-alloyed 7475 aluminum powders were mixed with ceramic particles and milled in a high energy planetary Fritsch ball mill for up to 40h. Subsequently, it was compacted at 380°C/600 MPa. The microstructure of the obtained composites was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The performed investigations proved that both types of composites show a good dispersion of ceramic phases. The composite matrix was characterized by fine grain size, i.e. less than 100 nm and contained a high density of even smaller, Zn, Cu or Fe rich precipitates. The EDS chemical analysis indicated local presence of MgO at the metal/ceramic interfaces in both types of composites. The presented approach allowed to produce a composite with AlN or Al2O3 particles in nano-crystalline aluminium alloy matrix.