Tensile Properties and Microstructure Evolutions of Low-Density Duplex Fe–12Mn–7Al–0.2C–0.6Si Steel

Abstract

An austenite-ferrite duplex low-density steel (Fe–12Mn–7Al–0.2C–0.6Si, wt%) was designed and fabricated by cold rolling and annealing at different temperatures. The tensile properties, microstructure evolution, deformation mechanism and stacking fault energy (SFE) of the steel were systemically investigated at ambient temperature. Results show two phases of fine equiaxed austenite and coarse band-like δ-ferrite in the microstructure of the steel. With increasing annealing temperature, the yield and tensile strengths decrease while the total elongation increases. At initial strains, the deformation is mainly concentrated in the fine austenite and grain boundaries of the coarse δ-ferrite, and the interior of the coarse δ-ferrite gradually deforms with further increase in the strain to 0.3. No twinning-induced plasticity (TWIP) or transformation-induced plasticity (TRIP) occurred during the tensile deformation. Considering element segregation and two-phase proportion, the chemical composition of austenite was measured more precisely. The SFE of the austenite is 39.7 mJ/m2, and the critical stress required to produce deformation twins is significantly higher than the maximum flow stress of the steel.

Effect of Grain Size on the Plastic Deformation Behaviors of a Fe-18Mn-1.3Al-0.6C Austenitic Steel

“…The results are shown in Figure 11. After annealing and rolling, annealed twins and mechanical twins were produced inside the samples, which had an orientation difference of 60 • from <111>, and they were ∑3 co-grid twins, which are marked by red lines on the image quality (IQ) maps [32,33].…”

The Influence of Cr Addition on the Microstructure and Mechanical Properties of Fe-25Mn-10Al-1.2C Lightweight Steel

“…The need to reduce vehicle weight in the automobile industry is driven by the goal of improving fuel efficiency and reducing carbon dioxide emissions. In the research of developing high-strength and lightweight steels, Fe-Mn-Al-C steels have gained attention for their advantages by combining excellent mechanical properties with a low density [1][2][3][4]. These steels can be categorized into fully ferritic, fully austenitic, ferrite-based duplex, and austenite-based duplex depending on their constitution phase [5][6][7][8].…”