Elastic-stiffness distribution on dual-phase stainless steel studied by resonance ultrasound microscopy

Distribution of the elastic stiffness coefficient in a dual-phase stainless steel is studied using resonance ultrasound microscopy and electron backscattering patterns. Using a monocrystal langasite oscillator, the resonance frequency change due to contact with the material is measured contactlessly using a solenoid coil antenna. A theoretical calculation based on the contact between two anisotropic bodies is proposed to determine the contact stiffness from the resonance frequency. The measured stiffness distribution is compared with that predicted from the orientation distribution determined using the electron backscattering-pattern method. They generally agreed but the stiffness determined by resonance ultrasound microscopy is nonuniform even in a single γ-phase grain. The nonuniformity of the chromium concentration can be a principal cause of the stiffness distribution.