High-temperature in-situ measurements of thermal vacancies in a TiAl intermetallic compound using a desktop positron beam

Abstract

A desktop positron beam apparatus combined with a β + -γ coincidence positron annihilation lifetime spectrometer was used for investigating thermal equilibrium vacancies in a TiAl intermetallic compound which is expected to find uses as a lightweight, heat-resistant structural material. The vacancy formation energy of the TiAl was derived from high-temperature in-situ measurements of positron lifetimes, and its value is in good agreement with a previously-reported value measured using a sophisticated internal positron source method. The measurement method used in this study makes it possible to investigate the vacancy formation energies in any material at high temperatures easily, even in unweldable ceramics, semiconductors, and brittle intermetallics for which conventional internal positron source methods cannot be applied.