Detection of Ti-rich precipitations in iron by means of positron annihilation spectroscopy

A possibility of detection of various Ti-rich precipitates in iron (steel) using positron annihilation spectroscopy is analysed. First, we investigate precipitates with sulfur (Ti9S9, Ti4C2S2), which have not been studied yet. We used the ab initio LMTO method and calculate positron affinities of all studied perfect systems. We also employ an improved supercell technique and atomic superimposed method and determine positron lifetimes for systems with vacancies. It turns out that even undefected Ti9S9 and Ti4C2S2 precipitates can bind a positron and, therefore, can be detected in positron annihilation experiments in contrast to TiC and TiN precipitates which can trap positrons only if they contain vacancies. (author). 15 refs, 4 tabs, 1 fig