In situ high-energy X-ray diffraction investigation of the micromechanical behavior of Fe-0.1C-10Mn-0/2Al steel at room and elevated temperatures

The micromechanical behavior of medium-Mn transformation-induced-plasticity (TRIP) steels with nominal chemical compositions of Fe-0.1C-10Mn (mass%) (0Al steel) and Fe-0.1C-10Mn-2Al (mass%) (2Al steel) fabricated by intercritical annealing 600 °C for 1 h and 650 °C for 1 h, respectively, was investigated using in situ high-energy X-ray diffraction (HE-XRD) with uniaxial tensile tests at 25 °C and 100 °C. We found that Lüders band propagation promoted lower volume fraction of austenite transformation to martensite in 0Al steel than 2Al steel at 25 °C while higher volume fraction of austenite transformation to martensite in 0Al steel than 2Al steel at 100 °C. Portevin-Le Châtelier (PLC) band propagation promoted higher volume fraction of austenite transformation to martensite in 0Al steel than 2Al steel during deformation at 25 °C and 100 °C. Moreover, the addition of Al obviously suppresses the formation of intermediate ε martensite during tensile deformation, thus the zigzag change in lattice strain of austenite was completely depressed in 2Al steel. Due to the controlled stability of metastable austenite, the 2Al steel demonstrated the best combination of ultimate tensile strength and total elongation at 25 °C.