Specimen Preparation for Transmission Electron Microscopy of Twins in B19′ Martensite of Ti–Ni Shape Memory Alloys

Abstract

Specimen preparation for transmission electron microscopy (TEM) of twins in B19' martensite in the edge-on state of polycrystalline Ti-Ni shape memory alloys was proposed utilizing the recrystallization texture of cold-drawn rod and the parent-martensite lattice correspondences. The five twinning modes, i.e. Type II, {111} Type I, {011} Type I, (100) compound and (001) compound twins, were observed in the martensite. The of the martensite which is derived from the of the parent phase is in the edge-on state for all the observed twinning modes, except for the (001) compound twinning. The of the martensite which also corresponds to the of the parent phase is in the edge-on state for the {011} Type I and (001) compound twinnings. There was the recrystallization fiber texture of the parent phase in the cold-drawn and subsequently annealed rod. Therefore, the identification of twinning modes by electron diffraction and the high resolution electron microscopy (HREM) study of twin boundaries in the edge-on state were easily performed using the specimen which was sliced obliquely about 50 degrees to the drawing axis of the rod.