In Situ Susceptibility Measurement of the Low Temperature Martensitic Transformation

An ac susceptometer was constructed in order to carry out in situ measurements of the susceptibility of stainless steel SUS316L specimens in tension tests under cryogenic temperatures. Changes in susceptibility are associated with the formation of a ferromagnetic ¿\´ phase due to a martensitic transformation induced by deformation at 4.2K. The observed susceptibility became larger as the load was removed during tension testing. The stress-induced magnetic anisotropy seems to lower the susceptibility of the specimen under tension. The "true susceptibility" derived from successive loading and unloading experiments is conjectured to reflect the proportion of martensite.