Effect of Heat Treatment on Microstructures and Tensile Properties of a Fe-1.7Mn-1.3Al-0.5C Steel

In this study, the main target is to obtain the better combination of strength and ductility by using heat treatments to adjust the microstructures of Fe-1.7Mn-1.3Al-0.5C steels. Effect of intercritical annealing (IA) and bainitic holding temperatures on the volume fraction and carbon content of retained austenite were evaluated by means of X-ray diffraction (XRD). Mechanical properties of the steel under different heat treatments processes were investigated by using uniaxial tensile tests. An excellent combination of strength and ductility has been obtained for the steel after intercritical annealing at 800°C for 120s and bainitic holding at 380°C for 300s, revealing a yield strength of 680 MPa, a tensile strength of 1200 MPa and a elongation-to-failure as high as 0.52. The steel mainly consists of ferrite, bainite, and retained austenite. The volume fraction of retained austenite is 28%, with a concentration as high as 1.71%, which enhances the mechanical stability of austenite and results in a good combination of strength and ductility.