Abstract: Annealing temperature of Fe-2.0Mn-4.7Al-0.4C steel was determined to be 860 ℃ by using JMatPro simulation software. The effect of annealing time on the microstructure and mechanical properties of the hot-rolled Fe-2.0Mn-4.7Al-0.4C steel was studied by means of optical microscope, scanning electron microscope, and electronic universal material testing machine. The results show that after annealing treatment, the microstructure of the hot-rolled Fe-2.0Mn-4.7Al-0.4C steel transforms from δ ferrite, α ferrite, martensite, pearlite, and cementite to δ ferrite, pearlite, and retained austenite. When annealed for 120 min, the tensile fracture morphology of the specimen shows a transition from brittle fracture to ductile fracture. The tested steel has the best comprehensive mechanical properties with tensile strength of 515.6 MPa, yield strength of 361.0 MPa, maximum elongation of 35.4%, and strength-elongation product of 18.3 GPa·%. However, when the annealing time is too long to reach 180 min, the grain grows and aggregates, the dislocation movement disappears, resulting in a decrease in material toughness and an increase in material brittleness. The fracture surface is mainly composed of ductile dimples and relatively smooth cleavage surfaces.

Key words: low density steel, annealing time, fracture morphology, microstructure, mechanical properties