TENSILE FRACTURE ANALYSIS OF Ni-Ti-Nb MEMORY ALLOY JOINTING RING WITH WIDE HYSTERESIS SHAPE

The fracture of Ni-Ti-Nb alloy ring with wide hystersis shape memory,is studied by tensile test. The fracture and microstructure of ring is analysed by SEM. It is found that the hard and brittle (Ti,Nb)2Ni phase leads to fracture of the ring. The (Ti,Nb)2Ni phase formation cause is analysed. It is proposed that these methods of multiple electric arc melting and thermal deformation are used to improve the quality of the alloy.