Effect of water jet cavitation on microstructure and superelasticity of NiTi shape memory alloy
In order to investigate the influence mechanism of water jet cavitation on the microstructure and properties of NiTi shape memory alloy,the water jet cavitation experiments were carried out in tap water with different exposure times.The microstructure,phase and properties of the samples were cha-racterized by using SEM,XRD,TEM,micro-Vickers hardness tester,nano-indentation instrument and laser confocal microscope.The results show that both the surface microhardness and superelasticity of NiTi shape memory alloy increase with the prolongation of cavitation time within 20 min.When the jet cavitation time is 15 min,a large number of dislocations appear in the NiTi shape memory alloy and the surface microhardness HV reaches the maximum value of 340.35(load is 0.245 N),which is about 34％higher than that of the original sample.The depth of the influence hardened layer of water jet cavitation on NiTi alloy is about 300 pm.The super elasticity of the alloy is measured by the nano-indentation energy recovery rate.The elastic energy recovery rate of the alloy increase from 38.25％to 45.70％after 15 min of waterjet cavitation,indicating that waterjet cavitation treatment can effectively improve the super elasticity of the sample.The increase in microhardness and super elasticity in NiTi shape memory alloy can be attributed to dislocation proliferation in the alloy.
万方数据
维普
