Abstract
Physical and mechanical properties of Fe-Al alloys are strongly influenced by atomic ordering and point defects. In the present work positron lifetime (LT) measurements combined with slow positron implantation spectroscopy (SPIS) were employed for an investigation of quenched-in vacancies in Fe-Al alloys with the Al content ranging from 18 to 49 at.%.
The interpretation of positron annihilation data was performed using ab-initio theoretical calculations of position parameters. Quenched-in-defects were identified as Fe-vacancies.
It was found that the lifetime of positrons trapped at quenched-in defects increases with increasing Al content due to an increasing number of Al atoms surrounding the Fe vacancies. The concentration of quenched-in vacancies strongly increases with increasing Al content from approximate to 10(-5) in Fe82Al18 (i.e. the alloy with the lowest Al content studied) upto approximate to 10(-1) in Fe51Al49 (i.e. the alloy with the highest Al content studied in this work).