Vacancy analysis with a positron microprobe for hydrogen embrittlement under elastic stress of tempered martensitic steels

Oshima, Nagayasu*; Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hirade, Tetsuya  

Studying the creation and time evolution of defects is an important issue for interpreting the hydrogen embrittlement mechanism of steels. We have been studied the relationship between hydrogen embrittlement of high strength steel and lattice defects associated with hydrogen by a positron probe microanalyzer (PPMA) which is positron lifetime measurement system with a pulsed positron microbeam. The results with the mean positron lifetime measurements indicated that vacancies or vacancy clusters were additionally formed with hydrogen embrittlement under elastic stress. We also have tried to see the detail of the change with hydrogen embrittlement by applying the multicomponent analysis of positron annihilation lifetime spectra. The results indicated a possibility that the vacancies were formed as the complex with dislocations.