ELECTRON-MICROSCOPY STUDY OF THE EUTECTIC STRUCTURE IN TI40NI40NB20 ALLOY

The Ti40Ni40Nb20 eutectic is an interesting material with respect to the applications of shape memory alloys. The eutectic, which consists of TiNi(B2) alpha phase and Nb-rich(bcc) beta phase, was studied by conventional and high resolution electron microscopy, and the following results were obtained. The morphology was invariably lamellar with the interface plane parallel to {110}(alpha)//{110}(beta). The orientation relationship was such that [100](alpha)//[100](beta) [010](alpha)//[010](beta) [001](alpha)//[001](beta) Thus, the equivalent directions and planes are completely parallel. Steps and facets on a larger scale were found along the interfaces, and the Burgers vectors of misfit dislocations were analyzed by the O-lattice theory.