Deformation Mechanism Investigation on Low Density 18Mn Steels under Different Solid Solution Treatments

To meet the demand of 10% weight reduction goal for automotive steel, microstructure and mechanical properties Fe-18Mn-Al-C steel with different carbon aluminum contents were investigated under solid solution treatments, deformation mechanisms experimental steels elucidated. Aided by thermodynamic calculation, transmission electron microscopy (TEM) in situ scanning microscope (SEM) analysis, it was shown that 18Mn-1.5Al about 20 mJ/m2 stacking fault energy (SFE), twinning-induced plasticity (TWIP) effect always dominated this after treatments tensile deformation. With 7 wt% addition, SFE austenite affected temperature range between 60 65 mJ/m2. The existence δ-ferrite obviously inhibited TWIP effect. increase treatment temperature, gradually transformed into austenite, n-value remained low stable a large strain range, which caused local hardening during Due to difference deformability structure as well inconsistent extension slip band, micro-cracks easily initiated 18Mn-7Al steel; then, exhibited lower plasticity.