Non-destructive evaluation of 304 stalinless steels using a scaaning hall-sensor microscope: visualization of strain-induced austenite-phase breakdown

摘要

using a scanning Hall-sensor microscope with an active area 50 mu m X 50 mu m, we succeeded in visualizing a breakdown of paramagnetic austenite-phase in 304 stainless steels induced by a plastic strain at room temperature, resulting from a transformation to frerromagnetic martensite-phase. magnetic images of spontaneous magnetic fields on a surface of strained sample show the degree and the place (and/or the extent) of phase breakdown. Futhermore, the images nearly agree with the calculated results for the principal shear stress rather than the principal stress under plastic deformation, indicative of the driving force of this breakdown. The study should open a way for non-destructive evaluation of 304 stainless steels.