Study On Processing, Microstructure And Property Of Biomedical TiNi Fine Wire

TiNi shape memory alloy possesses characteristics such as good SME, superelasticity and biocompactibility. With the development of TiNi shape memory alloy and interventional medicine, the research and application for TiNi fine wire has been a key area of applied exploitation for shape memory alloy. A systematic study of processing technology and microstructure and property of the Ti-50.7at%Ni shape memory alloy fine wire (Φ0.2mm) has been carried out in this paper. The foundation for practical production and application of the TiNi shape memory alloy fine wire has been provided. The main results of this paper are as follows:On the basis of study of TiNi shape memory alloy fine wire drawing process, appropriate processing parameters of drawing and die and lubricant have been gotten. TiNi materials by vacuum induction melting have been made into wire of Φ0.1mm using forging, rolling and hot drawing. Pass process rate of hot drawing was 10%~20%. Tempreture of furnace was 550℃~750℃. For hot drawing TiNi wire of Φ0.3mm ~ Φ1.0mm, die of tungsten carbide alloy was appropriate. For hot drawing TiNi fine wire of Φ0.1mm~Φ0.3mm, die of diamond was appropriate. When graphite lubricant of low friction coefficient was used, problems of fine wire sticking die easily and surface quality of thick wire have been controlled. The properties of TiNi shape memory alloy fine wire accord with the demonds of biometical TiNi alloy( σ_b≥551MPa, Ψ ≥10%).Based on the experimental result of DSC and SEM of TiNi shape memory alloy fine wire, effect of heat treatment on microstructure and phase temperature of TiNi alloy fine wire has been investigated. During heat-treatment, Ti3Ni4 were precipitated. Precipitates increase with the increase of heat-treatment temperature and time. Phase transformation temperatureincreases with the increase of heat-treatment temperature and time.Based on the experimental result of bending test of TiNi shape memory alloy fine wire, effect of heat treatment on shape memory effect of TiNi alloy fine wire was gotten. The biggest shape memory strain of TiNi alloy fine wire increases slightly with the increase of heat-treatment temperature. With the increase of time at the same temperature, the biggest shape memory strain decreases slightly. Fatigue life of specimens shortens with the increase of bend strain. Fatigue life increases with the increase of heat-treatment temperature. Fatigue life of specimen heat-treated at 500 ℃ was best, which was 4380.Based on the experimental result of tension test of TiNi shape memory alloy fine wire, effect of heat treatment on superelasticity of TiNi alloy fine wire was defined. TiNi alloy fine wire had complete superelasticity. Superelasticity strain of TiNi alloy fine wire heated at 500℃ for 30min was biggest, which was 8%.