Fundamental Deformation and Recovery Behaviors of Ni-Ti-Nb Shape Memory Alloy

Abstract

Fundamental deformation and deformation-recovery behaviors of Ni-Ti-Nb shape memory alloy were experimentally investigated, especially their dependency on test temperature. Monotonic tension tests and deformation-recovery tests were conducted at low and high temperatures ranging from 253 K to 473 K. Stress-strain response above 323 K is quite different from that below the temperature. The yield stress shows the positive temperature-dependency below 323 K and the opposite trend is observed above this temperature. From this result, it is estimated that the dominant mechanism of inelastic deformation is the plastic deformation above 323 K and the pseudo-elastic one below it. The temperature at which strain recovery starts strongly depends on the maximum prestrain and prestraining temperature. Residual strain is always observed in the deformation-recovery tests. Also it is found that the larger recovery strain can be obtained for the larger prestrain and at the lower prestraining temperature.