Microstructure and tensile behavior of duplex low-density steel containing 5 mass% aluminum

The microstructure and tensile behavior of low-density steels containing 5 mass% Al were investigated. An alloy obtained under a specific heat treatment condition showed deformation-induced martensitic transformation, which yielded excellent mechanical properties of a high tensile strength of >900 MPa and a high total elongation of >50%. The volume fraction and grain size of the austenite depended on the annealing temperature, which resulted in a transition from stable to metastable behavior of the austenite. The effects of solute content on grains and of austenite grain size on stability were discussed.