ELECTRON-MICROSCOPY STUDY OF THE EUTECTIC STRUCTURE IN TI40NI40NB20 ALLOY

The Ti40Ni40Nb20 eutectic is an interesting material with respect to t he applications of shape memory alloys. The eutectic, which consists o f TiNi(B2) alpha phase and Nb-rich(bcc) beta phase, was studied by con ventional and high resolution electron microscopy, and the following r esults 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)//[0 10](beta) [001](alpha)//[001](beta) Thus, the equivalent directions an d planes are completely parallel. Steps and facets on a larger scale w ere found along the interfaces, and the Burgers vectors of misfit disl ocations were analyzed by the O-lattice theory.