The fracture behaviors in an Fe–Mn–Al alloy during quenching processes

Abstract

The Fe–Mn–Al alloy with a composition of Fe–23.0 wt.% Mn–7.4 wt.% Al–0.03 wt.% C is single BCC phase at 1373 K, and is dual phase with BCC and FCC phase at 1323 K. When the alloy is quenched from 1373 K into cold brine, the effect of thermal stress results in intragranular fracture of the BCC phase. While the Fe–Mn–Al alloy is quenched from the BCC+FCC dual phase region at 1323 K into cold brine, the FCC phase undergoes plastic deformation in lowering the tensile thermal stress of BCC grains, and this result minimizes the fracture behavior of BCC grains. However, when the grain size exceeds a critical value, and the maximum plastic deformation of the FCC grains fails to effectively reduce the effect of thermal stress, quenching from 1323 K leads to cracking in this type of dual phase structure. According to our analysis based on the theory of the approximate thermal stress, we can be certain that the maximum tensile stress of the specimen occurs at the quenching moment and at a location near the center of the specimen surface. This theoretical analysis is consistent with experimental results. In a dual phase structure containing both brittle and ductile phases with fine grain sizes, if the minor ductile grains can effectively link the major brittle grains, it is not likely such materials will experience fracture behavior during quenching.