Role of strain-induced martensitic phase transformation in mechanical response of 304L steel at different strain-rates and temperatures

The strain-rate and temperature dependencies of the strain-induced martensitic phase transformation (MPT) of AISI 304 L are experimentally investigated. Firstly, the tensile tests of 304 L at room temperature are conducted at the strain-rates ranges from 6.67 x 10(-4) s(-1) to 80 s(-1). The stress-strain curves indicate a significant strain-rate effect of the strain-induced MPT, which is closely relevant to extent of the adiabatic heating. The second batch of tensile tests are conducted at several representative strain-rates and at different temperatures ranging from 0 degrees C to 100 degrees C. The martensitic volume fractions at different plastic deformation stages are measured by X-ray diffraction to trace the evolution of martensitic phase in the tests. The test results indicate that the environmental temperature and the strain-rate exert coupling influence on the stress-strain behavior. Variations in strength and ductility of 304 L in the tests are explained with a competition mechanism between strain-induced MPT, thermal softening and strain-rate strengthening. A kinetic model of MPT is modified to take the strain-rate, initial temperature and temperature rise into account.