Effect of Solution Treatment Temperature on Microstructure and Properties of Fe-0.72Mn-3.7Al-0.53C Low-Density Cast Steel

In the present research, the microstructure and mechanical properties of low-density Fe-0.72Mn-3.7Al-0.53C steel were investigated after solution treatment at 900 °C, 1000 °C, 1110 °C and 1200 °C for 1 h. The density of steel is about 7.0 g·cm−3 due to the addition of a higher content of aluminum elements. The microstructure was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanical behavior was analyzed by room temperature tensile testing. The results show that the microstructure of the steel is ferrite and martensite after solution treatment, and that martensite can be divided into dislocation martensite and twinned martensite according to different substructures. Part of the martensite grows in a mirror-symmetrical manner in order to adjust the strain energy that increases with the system undercooling to form twinned martensite. After solution treatment at different temperatures, the tensile strength and elongation of the steel increased and then decreased with the increase of the solution treatment temperature, and the tensile strength could reach 928.92 MPa, while maintaining excellent toughness and elongation at 5.89%.