Fe元素对TiNi形状记忆合金相变点和力学性能的影响

采用纯度均为99%的Ti,Ni和Fe原材料,在真空电弧炉中熔炼5次,制备出TiNiFe(Fe=2 5%,3 0%和3 5%)3种成分的TiNiFe合金铸锭,经850℃保温24h的真空均匀化处理后,锻造成 7mm的棒材。采用光学金相、电阻法和拉伸试验等方法研究了Fe含量对TiNi形状记忆合金晶粒度、相变温度和力学性能的影响。随着Fe的原子含量由2.5%提高到3.5%,TiNiFe合金的晶粒略有细化,晶粒大小从49μm减小到26μm,马氏体相变温度从-73.5℃下降到-190.0℃以下,抗拉强度和屈服强度也显著提高,延伸率δ没有明显变化。所研制的TiNiFe合金的马氏体相变温度和室温力学性能可满足航空管接头用记忆合金的要求。

Influence of Fe Addition on Phase Transformation Temperatures and Mechanical Properties of TiNi Shape Memory Alloys

Polycrystalline ingots of TiNiFe(Fe=2.5%, 3% and 3.5%) shape memory alloys are prepared by arc melting repeated for five times with high purity element (99%) under argon atmosphere. After homogenizing at 1123 K for 24 hours in a vacuum quartz ampoule, the alloys are forged into rods with 7 mm in diameter. The influence of Fe content on the grain size, phase transformation temperature and mechanical property of TiNi shape memory alloys are studied by optical microscope observation, electrical resistance measurement and mechanical tensile test, respectively. The results show that with the increase of Fe content from 2.5% to 3.5%, the grain size deceases from 49μm to 26μm and the martensite transformation temperature decreases from -73.5℃ to-190℃, and, moreover, the yielding strength and tensile strength are remarkably improved, while the percentage elongation changes a little. The martensite transformation temperature and mechanical properties of TiNiFe alloy satisfy the requirements of pipe coupling in aviation application.