Detectability of stress-induced martensite phase in ferromagnetic shape memory alloy Fe–30.2at.%Pd by Barkhausen noise method Original Research Article

The possibility to detect the phase transformation of stress-induced martensite in ferromagnetic shape memory alloy Fe–30.2at.%Pd thin foil was investigated by using Barkhausen noise (BHN) method. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twin in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.