Microstructural evolution in mechanically alloyed Al-heavy-metal oxide composites

Structural observations of mechanically alloyed Al–MnO2, Al–HfO2 and Al–WO3 composites were performed by means of transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The distribution of the constituent elements was tested in X-ray energy-dispersive spectroscopy (EDS). Samples of the as-extruded material were annealed at 873 K for various times. The microstructure changed due to a solid-state reaction between the Al-matrix and heavy-metal oxides. The distribution of oxygen was analyzed by EDS across oxide/matrix boundaries in order to test an Al-matrix oxidation nearby pre-existing oxide particles. X-ray diffraction analysis revealed an intermetallic grain growth after long annealing times.