Factors affecting deformation induced martensitic transformation of SUS304 stainless steel

Tensile tests of SUS304 stainless steel specimens were performed with different strain rates at different temperatures.Moreover, the martensite induced by deformation was analyzed by ferrite measuring instrument, optical microscopy and XRD.Experimental results show that the transformation of martensite is closely related to uniformity of microstructure, strain rate and temperature.At room temperature, the amount of martensite induced by deformation increases with the increasing of tensile strain.For the tailor-welded tube endured 30% circumference strain in hydroforming process at temperature, the amount of martensite is higher in fusion zone than that in HAZ, and it is fewer in the base metal, i.e., the higher the uniformity, the less the amount of martensite transformation induced by deformation from austenite.The amount of martensite decreases with the increasing of testing temperature.Tensile tests at 275℃ indicated that martensite transformation induced by deformation can be restrained in the process of plastic deformation at this temperature, the volume fraction of martensite is almost 0 under such conditions.