The effect of rolling and subsequent aging on microstructures and tensile properties of a Fe-Mn-Al-C austenitic steel

The influence of rolling and subsequent aging on the microstructures and tensile properties of an austenitic Fe-23.38Mn-6.86Al-1.43C-0.038Nb-0.29Mo steel was systematically investigated. After hot rolling, the average grain size decreases; the microstructures are heterogeneous due to coarse grains surrounded by fine grains together with the formation of three-types of sub-micron particles along the grain boundaries. Additionally, nanosized kappa-carbides consist of large ones mainly located in the vicinity of tangled dislocations and ultra-fine ones evenly distributed in the matrix. Consequently, the strength is significantly increased after rolling. With increasing the rolling reduction from 20% to 60%, the strength gradually increases but ductility decreases primarily due to an increased dislocation density. Meanwhile, the size and number of the relatively large kappa-carbides are reduced and the distribution of kappa-carbides is gradually homogenized, which affect the strain hardening rate. After subsequent aging at 550 degrees C, intra-granular kappa-carbides are coarsened, leading to an increase in the strength and a decrease in the ductility. The well balance between the kappa-carbides precipitation and the dislocation recovery contributes to the optimized tensile properties after rolling at a reduction of 40% and subsequent aging at 450 degrees C.

Automated summary

After rolling, the strength of the steel significantly increases, while the ductility decreases primarily due to an increased dislocation density. The strength gradually increases with decreasing rolling reduction, but the size and number of relatively large kappa-carbides decrease.