An Experimental Study on Strain Rate Sensitivity of Strain‐induced Martensitic Transformation in SUS304 by Real‐time Measurement of Relative Magnetic Permeability

摘要

>With excellent mechanical properties because of strain‐induced martensitic transformation (SIMT), applications of austenitic stainless steels can be extended to a further broad range of engineering fields. In order to discover applications from a clarification of their mechanical properties, especially at higher deformation rate, it is important to evaluate an amount of martensite, which can control such excellent performances of the steels during deformation. However, until now, it is quite hard to find experimental studies for the evaluation during deformation at various strain rates. In the past, volume resistivity and impedance have been measured during deformation. However, these studies have not been successful to evaluate it with a higher precision. Instead of those, it is useful to measure directly relative magnetic permeability, which has a correlation with the amount of martensite, because of focusing on a ferromagnetic characteristic of martensite. In this study, at first, SUS304, which is a kind of austenitic stainless steels, is deformed plastically under tension at various strain rates. Then, it is attempted to evaluate the amount of martensite during deformation by measuring the relative magnetic permeability expressing ferromagnetism directly. Finally, the strain and strain rate sensitivity of SIMT in the steel is discussed by obtained results.