2005 年 17 巻 1+2 号 p. 146-152
The possibility of detecting the phase transformation of stress-induced martensite in a ferromagnetic shape memory alloy Fe-30.2at%Pd thin foil was investigated by using the Barkhausen noise (BHN) method. Stress-induced martensite twining was observed by laser microscopy above a stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twining in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to the austenite phase at weak magnetic fields. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field levels. The BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.
