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. <011>Type II, {11I} Type I, {011} Type I, (100) compound and (001) compound twins, were observed in the martensite. The <011> of the martensite which is derived from the <001> of the parent phase is in the edge-on state for all the observed twinning modes, except for the (001) compound twinning. The <100> of the martensite which also corresponds to the <001> of the parent phase is in the edge-on state for the {011} Type I and (001) compound twinnings. There was the <111> 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.