The microstructures and mechanical properties of an austenitic Nb-bearing Fe–Mn–Al–C alloy processed by controlled rolling

The mechanical properties of a Fe–Mn–Al–C based austenitic alloy were improved by employing controlled rolling. An experimental alloy, having a composition of Fe–28Mn–9Al–0.5Mo–0.7W–0.55Nb–1.0C (wt.%), was prepared and controlled-rolled in four passes at temperatures between 1000 and 900°C, after annealing at 1200°C for 2 h. The controlled-rolled alloy was then subjected to aging treatments at 550°C for various times. The microstructural characteristics were examined by light, scanning electron and transmission electron microscopy. The mechanical properties were investigated by means of hardness measurements and tensile tests. The as-controlled-rolled alloy consisted of unrecrystallized austenite grains with deformed annealing twins, subgrain boundaries and deformation bands, and contained a high density of dislocations as well as dense dispersion of fine Nb(C,N) carbo-nitrides in the matrix. Subsequent aging treatments of the controlled-rolled alloy showed age hardening similar to that reported for the solution-treated alloys. The strengthening of the experimental alloy due to the controlled rolling and aging is discussed on the basis of microstructural observations.