NiTiNb形状记忆合金的应力松弛研究

Study on Properties of Stress Relaxation for NiTiNb Shape Memory Alloy

为了解NiTiNb形状记忆合金的高温松弛性能,进行了高温下的松弛试验。由应力松弛与蠕变的关系,推导得到松弛曲线表达式。通过实验数据回归,发现松弛曲线表达式与实验结果吻合良好,并得到了表征材料抗松弛性能的材料松弛特征系数和剩余应力比。结果表明,温度越高,初始应力越大,应力松弛越明显;当温度在300～400℃,初始应力在260～360MPa时,NiTiNb的应力松弛很小;在高温下NiTiNb的抗松弛性能优于NiTiFe,更适合于高温下使用。

Stress relaxation tests at high temperature are performed for NiTiNb shape memory alloy to obtain the properties of stress relaxation .The relaxation curve fitted with the expression , which is deduced based on the relation between the relaxation and the creep. With the aid of experimental data , relaxation characteristic coefficient and remaining stress ratio are obtained, which characterize the relaxation behavior. The results of the study show that stress relaxation would be more evident with the higher temperature and/or greater initial stress . NiTiNb alloy has good relaxation resistance in the temperature range 300～400℃ and the initial stress range 260～360MPa. NiTiNb has better properties to resist relaxation than NiTiFe,therefore it is more applicable to work at high temperature.