An experimental study on strain-induced martensitic transformation behavior in SUS304 austenitic stainless steel during higher strain rate deformation by continuous evaluation of relative magnetic permeability

In the past, it is experimentally revealed that the stacking fault energy (SFE) for the strain-induced martensitic transformation (SIMT) in metastable austenitic stainless steels is positively dependent on the strain rate, especially at impact strain rate; however, a conflicting view is recently reported that it is independent on the strain rate. To solve the conflict on the rate sensitivity of SFE, a non-destructive method to determine the martensitic volume fraction precisely under quasi-static tensile loading is effective and a method for measuring the relative magnetic permeability using AC voltage has been previously developed. However, this technique overestimates magnetic permeability during impact testing due to the eddy current generated at high frequencies, which can be avoided by applying DC voltage to the primary coil. In this work, quasi-static and impact tensile tests are performed on commercial SUS304 metastable austenitic stainless steel at various strain rates to determine its relative magnetic permeability during deformation. The obtained experimental data are utilized to investigate the SIMT behavior of SUS304 steel under quasi-static and impact tensions. As a result, it successfully captures the SIMT behavior in SUS304, especially during high strain rate deformation and the role of SFE on SIMT at higher strain rate is discussed.