塑性ひずみ誘起された準安定オーステナイト系ステンレス鋼の非線形超音波特性, 磁気特性と結晶方位差の関係

抄録

We studied the correlation between the evolutions of non-linear acoustic and magnetic properties and local misorientation on strain-induced martensitic transformation (SIMT) behavior in SUS 304 metastable austenitic stainless steel during tensile test. Two nonlinear acoustic characterizations; resonant frequency shift and high harmonic components with electromagnetic acoustic resonance (EMAR), parameters in magnetic hysteresis loops were measured. Furthermore, the evolution of microstructure was observed with electron backscatter diffraction (EBSD) was examined. EMAR is a contactless resonant method with an electromagnetic acoustic transducer (EMAT). This method enables not only to measure exact ultrasonic attenuation of measured sample but also to eliminate nonlinear acoustic effect between the sample and transducer. We used two type of axial SH wave EMATs, which transmit and receive axially polarized shear wave along a cylindrical surface of a circular rod, for ferromagnetic and non-ferromagnetic materials. The changes in non-linear acoustic and magnetic properties have good correlations with microstructural observations. They successfully capture SIMT behavior in a metastable austenitic stainless steel.