Ti-content dependence of transformation pseudoelastivity characteristics of TixNi(92−x)Cu8 shape memory alloys

Ti-content dependence of transformation pseudoelasticity (superelasticity) characteristics of TixNi(92−x)Cu8 (at.%)(X=49.0–51.0) alloys was investigated for the specimens annealed at 673 and 773 K, respectively. It was found that the maximum of recovery strain of the alloys with the composition of near 50.0at.%Ti is larger than those of the alloys with the composition of Ti-poor and Ti-rich content. The stress-hysteresis increases with decreasing Ti-content in the range of 49.0–50.0at.%Ti, but it keeps almost constant in the range of 50.0–51.0at.%Ti. The specimens annealed at 773 K exhibit stronger Ti-content dependence of stress-hysteresis and maximum of recovery strain than those annealed at 673 K do. The critical stress for slip exhibits little dependence on Ti-content for both the specimens annealed at 773 and 673 K. The above phenomena are attributable to the effect of two types of precipitates and remained dislocations in the alloys.