Nature and morphology of oxide particles in internally oxidised CuAl alloys

Abstract

The dispersed phases produced by two different methods of internal oxidation of Cu−0.035 wt.% Al single crystals were studied by electron diffraction. The Rhines pack method of internal oxidation gave a bimodal distribution of large 500–1000 Å triangular γ-alumina plates and small sub-150 Å ordered α-alumina particles. However, in single crystals oxidised by the two-furnace method two distinct regions were visible. The central region contained only small particles identical with those observed in the Rhines pack crystals. The outer section, covering 10–20% of the cross-section of the crystal, contained a coarse distribution of thin faceted α-alumina platelets, 1–5 μm in diameter. These α-alumina platelets were ordered and contained a high density of antiphase boundaries or shear faults.