Hot ductility and fracture mechanism of Fe-22Mn-0.7C TWIP steel

The static tensile behaviors of Fe-22Mn-0.7C TWIP steel and Q235 steel between 700 ℃ and 1300 ℃ were investigated by Gleeble-1500 thermo-mechanical simulator.The microstructure characteristic and fracture morphology were observed by optical microscopy,scanning electron microscopy,energy dispersive spectrometry and electron probe micro-analysis.The hot ductility and influenced mechanism were revealed based on the discussion of chemical composition,matrix phase volume fraction,grain size and solidification defects.It is found that the TWIP steel has a reduction in area lower than 40% in the temperature range of 700 ℃ to 1250 ℃,but its tensile strength is higher than that of Q235 steel.Fractographic results manifest intergranular fracture for the TWIP steel.Grain refinement and microsegregation descending in the TWIP steel are beneficial to increasing the hot ductility due to the improvement of matrix homogeneity.Besides,the tensile strength and reduction in area of the TWIP steel increase with increasing strain rate.