Abstract
Hardness of Fe-Al alloys shows a non-trivial dependence on chemical composition and thermal treatment of samples and cannot be fully explained by consideration of intermetallic phases formed according to the equilibrium phase diagram of Fe-Al system. Hardening in Fe-Al alloys caused by quenched-in non-equilibrium vacancies was studied in this work.
Non-equilibrium vacancies introduced into the alloys by quenching from 1000 degrees C were detected by means of positron annihilation spectroscopy. The concentration of quenched-in vacancies was found to strongly increase with increasing Al content from approximate to 10(-5) at.(-1) in the alloy with c(Al) = 18 at. % up to approximate to 10(-1) at.(-1) in the alloy with c(Al) = 45 at. %.
Comparison of the vacancy concentration and the Vickers microhardness revealed that hardening is proportional to square root of concentration of quenched-in vacancies.