Papers by Keyword: Titanium-Nickel Alloy

Abstract: In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed based on the tensile deformation properties of the existing copper and the TiNi rolled-SMA. The fatigue properties of both materials were also investigated by the plane-bending fatigue test. The results obtained can be summarized as follows. (1) The modulus of elasticity and the yield stress for the cast and rolled SMAs are lower than those for the copper. Therefore, the conventional rolled-SMA spatula and the new cast-SMA spatula can be bent easily compared to the existing copper-brain spatula. (2) With respect to the alternating- and pulsating-plane bending fatigue, the fatigue life of both the copper and the SMAs in the region of low-cycle fatigue is expressed by a power function of the maximum bending strain. The fatigue life of the conventional rolled SMA and the new cast SMA is longer than that of the existing copper. The fatigue life of the new cast and rolled SMAs in the pulsating-plane bending is longer than that in the alternating-plane bending. (3) The fatigue life of the rolled-SMA and the cast SMA for alternating- and pulsating-plane bendings can be expressed by the unified relationship with a power function of the dissipated work.

Abstract: We have studied diffuse scatterings appearing in Ti-(50-x)Ni-xFe (x = 6, 7, 8, 10) alloy, which shows negative temperature coefficient in electrical resistivity below a temperature Tmin. Electron diffraction pattern of each alloy exhibits diffuse scatterings below Tmin on cooling. The intensity maximum of the diffuse scatterings is located at an incommensurate position of g+<ζζ0>, where g represents reciprocal lattice points of the B2-phase. The value ζ is slightly smaller than 1/3 and decreases with increasing Fe content. The diffuse scatterings of the present alloys are well explained by the nesting effect of the Fermi surface in the B2-type structure, i.e., ζ of each alloy agrees with the length of nesting vector in the [110] direction, which is evaluated by a first-principle calculation.

Abstract: The characteristics of energy storage and dissipation in TiNi shape memory alloys were investigated experimentally based on the superelastic properties under various thermomechanical loading conditions. The results obtained can be summarized as follows. (1) The recoverable strain energy increases in proportion to the rise in temperature, but the dissipated work per unit volume depends slightly on temperature. In the case of low strain rates, the recoverable strain energy and dissipated work do not depend on both the strain rate and the temperature-controlled condition. (2) In the case of high strain rates, while the recoverable strain energy decreases and the dissipated work increases in proportion to the rise in strain rate under the temperature-controlled condition, the recoverable strain energy increases and the dissipated work decreases under the temperatureuncontrolled condition.