Effect Of Ageing Treatment On The Transformation And Mechanical Behaviour Of Rich-Ni NiTi Alloy

NiTi alloy relies on shape memory effect, superelastic and excellent biocompatibility, which makes it become the ideal choose for the medicine and industry. Considering that there are significant relationship between transformation and mechanical behaviour of NiTi alloy and thermal treatment and tensile temperatures, therefore, to study the effect of heat treatment and tensile condition are very important for NiTi alloy to understand the transformation and mechanical behaviour.This paper is respond to the effect of transformation and mechanical behaviour of Rich-Ni NiTi alloy with ageing treatment, which research mainly includes three parts: the effect between ageing temperatures and cycling ageing on transformation behaviour of Rich-Ni NiTi alloy; the relationship between ageing temperatures and mechanical of NiTi alloy and the effect of ageing treatment on the transformation mechanism.Firstly, to adopt DSC acquires the data of transformation temperatures, transformation heat and transformation consequence through analyzing DSC results so that attains the transformation behaviour of Rich-Ni NiTi alloy in diverse ageing temperatures. Likewise, analyzing results of cycling ageing treatment obtains the relationship between transformation behaviour and cycling ageing. The results of research shows that there are different transformation behaviour and transformation consequence for NiTi alloy in different ageing temperatures. In addition, We utilize the tensile machine of Instron 3365 to test mechanical behaviour of ageing NiTi which has different ageing temperatures and tensile temperatures and then analyze the relationship between them. The reaearch shows that there are different tensile behaviour for NiTi alloy samples which have different ageing temperatures in the same tensile temperature, with superelasticity, partial superelasticity and shape memory effect. The samples of NiTi alloy need larger induce stress to induce martentistical transformation with increasing of tensile temperatures. When the tensile temperatures research a unfixed value, the superelasticity of NiTi alloy will vanish. Finally, to use XRD analyzes the kinds of precipitation for specimen of NiTi, which has different ageing statement. The results show that the precipitation is Ni₄Ti₃ when the ageing temperature is underneath 833 K, when the ageing temperature is between 833 K and 923 K, the precipitation is Ni₃Ti₂, when the ageing temperature is between 923 K and 1000 K, the precipitation is Ni₃Ti, there is no precipitation when the ageing temperature is beyond 1000K.