Properties and microstructure of TWIP steel used in automobiles

25Mn-3Si-3Al TWIP steel sheets were developed by hot rolling, cold rolling and annealing treatment processing. The mechanical properties, microstructure and fracture mechanism of the sheets were investigated and the crystal textures were confirmed by X-ray diffraction measurement. The results show that the fracture mechanism of the sheets is typical toughness fracture under the condition of tensile failure, and the microstructure is austenitic with a large number of annealing twins before tension. During tension the annealing twins change into deformation twins, which make the strength and plasticity of the sheets increase. The textures formed during annealing treatment are advantageous to the plasticity of steel sheets.