Positron annihilation study of Al63Cu25Fe12 as a function of thermal treatment

A polycrystalline sample of Al63Cu25Fe12 has been studied as a function of thermal treatment by positron annihilation and X-ray diffraction techniques. Results suggest the presence of an icosahedral-to-rhombohedral microcrystalline phase transition near 300-degrees-C. Below this transition, a large increase in the annihilation line shape parameter S is observed, indicating significant localisation of the annihilating positrons. Above the transition, a small elevation in the S parameter value persists up to approximately 700-degrees-C. These results are discussed in terms of possible structural changes in the sample.