Effect of Pre-deformed Temperature on Recovery Property of Ni₄₇Ti₄₄Nb₉ Alloy Φ8mm Pipe Joint

The effect of pre-deformed temperature on memory recovery properties of Ni₄₇Ti₄₄Nb₉ alloy pipe joints was studied by using the methods of expanding diameter at low temperatures and water bath heating. The results showed that the transformation hysteresis and residual strain in internal diameter of Φ8mm pipe joints increased firstly and then decreased with the rise of the pre-deformed temperature in the pre-deformed temperature range of-55~-90℃. Transformation hysteresis and residual strain reached the maximum values 122℃ and 1. 3% respectively when the pre-deformed temperature is-65℃. At the same time,the elastic strain of inner diameter,radial recoverable strain and recovery rate decreased firstly and subsequently increased with the rise of the pre-deformed temperature. Consequently,the elastic strain reached the minimum value 1. 0% at the pre-deformed temperature-65℃. Otherwise, the radial recoverable strain and recovery rate can get the higher value 8. 6% and 86. 5% respectively,when the pre-deformed temperature is-65℃. Conclusion demonstrated that in order to obtain the wide transformation hysteresis and high recovery stress,the optimum pre-deformed temperature of Φ8mm pipe joint should be determined as-65℃.