Electropolishing conditions for trace analysis of B19′ martensite in Ti–Ni shape memory alloys

The electropolishing conditions of thin foil specimens for the crystallographic analysis of the B19′ martensite in the Ti–Ni shape memory alloy have been investigated. The specimens are electropolished between the martensite-start and the martensite-finish temperatures in three electrolytes; H2SO4–CH3OH, HNO3–CH3OH and HClO4–(CH3CO)2O. The traces of the martensite morphology are clearly retained on the foil surface polished in the HNO3–CH3OH solution. The microreversibility of the martensite morphology during in situ cooling experiments in the transmission election microscope is examined in the obtained foil. No microreversibility is observed in the foil. In order to confirm the validity of the residual traces for the crystallographic investigation of the martensite morphology, a preliminary analysis based on the lattice correspondence between the B2 and B19′ structures is carried out.