Study On The Friction Behavior Of Niti Shape Memory Alloy Under Various Temperatures

By using an atomic force microscopy, the micro-friction behavior of superelastic (SE) and shape memory effect (SME) NiTi alloy was investigated under various temperatures in vacuum environment. On one hand, the friction property of SE NiTi alloy was experimentally investigated by measns of single-scratch friction under both low and high loads at different temperatures. The study was focused on the effect of temperature-dependent stress-induced martensitic transformation on the topography and friction behavior. On the other hand, the friction property of SME NiTi alloy was investigated under reciprocating scratch at various temperatures. The friction force during the scratch tests and the residual depth in SME NiTi alloy were measured under different conditions. To understand the friction mechanism of SME NiTi alloy, the measured friction was divided into two component parts as interfacial friction and plough friction. The variation of each part of friction with the number of the scratch times was measured and discussed. The main conclusions of the paper can be summarized as following:1. Under wearless condition at low loads, the topography of both SE and SME NiTi alloy reveals temperature independent. The adhesion-dominated friction of SE and SME NiTi alloy is also temperature independent.2. Under high loads, scratch marks appears after friction on the surface of SE NiTi alloy. With the increase in temperature, the scratch marks get more narrow and shallow due to the increase in the transformation stress of SE NiTi alloy. At the same time, the plough-dominated friction decreases with the increase in temperature. Under reciprocating scratch tests at high load,, SME NiTi alloy shows SE effect at high temperature and the residual depth of scratch can be partially recovered. It is found that the depth of scratch generated at high temperature is almost the same as the one generated at room temperature after recovering by heating. 3. Under reciprocating scratch at high load, the interfacial friction of SME NiTi alloy increases and the plough friction decreases with the increase in the number of scratch cycles. Based on a simple contact analysis, the calculated friction is considerably accordant to the measured value.