Effect of chromium ternary additions on the ordering behaviour in Fe–28 at.% Al alloy

The ordering iron aluminide alloys such as Fe3Al and FeAl which exhibit D03 and B2 ordered structures have received considerable attention for their unique properties and wide range of applications. It is well-known that the mechanical properties are a function of the order degree of the materials; therefore, it is important to know the effect of ternary additions on the ordering behaviour of these materials for improving the mechanical properties by alloying elements. The aim of the present study was to investigate the chromium addition effect on B2 → D03 order transition utilizing differential scanning calorimetry (DSC), dilatometric analysis and microhardeness measurements and to estimate the activation energy and the Avrami exponent n of D03 phase. The thermal analysis and the determination of kinetics parameters of Fe–28 at.% Al–2 at.% Cr and Fe–28 at.% Al–5 at.% Cr alloys have shown that the effects of chromium addition are to stabilize the B2 ordered phase and to make the B2 → D03 transition slower than in the binary Fe–28 at.% Al alloy.