Study of defects in Fe-Re and Fe-Mo alloys by the Mossbauer and positron annihilation spectroscopies

The room temperature positron annihilation lifetime spectra and Fe-57 Mossbauer spectra were measured for pure Fe as well as for iron-based Fe1-xRex and Fe1-xMox solid solutions with x in the range 0.01 <= x <= 0.05. The measurements were performed in order to learn more about creation of structural defects during formation and further mechanical processing of the iron systems under consideration. The spectra were collected at least twice for each studied sample synthesized in an arc furnace-after cold rolling to the thickness of about 40 mu m well as after subsequent annealing at 1270 K for 2 h. It was found that in the annealed samples positrons live much shorter than in the not annealed ones which suggest that the latter samples are more defected as it could be expected. Moreover simultaneous analysis of the positron and Mossbauer data shows that cold rolling leads to creation of two types of defects. It seems that they are dislocations and vacancies. Finally from the Mossbauer data it follows that vacancies are located mainly in the vicinity of non-iron atoms, Re or Mo. This speaks in favour of the suggestion that in iron matrix the impurities mentioned above and vacancies interact attractively which supports the known from the literature, theoretical calculations on the Mo-vacancy interaction in iron. (C) 2012 Elsevier Ltd. All rights reserved.