利用BaZrO3坩埚制备钛镍形状记忆合金组织及性能的研究

Property and Microstructure of TiNi SMA Prepared Using BaZrO3 Crucible

摘要:

TiNi形状记忆合金由于其优良的合金性能,而成为商业化应用最为广泛的形状记忆合金。本文利用25公斤级自制 BaZrO₃坩埚制备了49.3Ti-Ni (at.%)合金,并将铸态合金加工成为直径为1mm的丝材。并利用XRD、氮氧化物分析仪等分析测试手段对的合金的化学成分及物相组成进行研究分析,利用扫描电镜、光学显微镜对合金的显微组织进行观察,利用两台自制设备对合金丝材的形状记忆回复率及疲劳性能进行分析测试,实验结果表明,利用BaZrO3坩埚对制备的钛镍合金的氧、氮含量能够分别达到560ppm和17ppm,杂质元素含量满足ASTM对于医用植入物以及医疗器械的标准要求；相比于真空电弧熔炼,利用BaZrO3坩埚感应熔炼制备的TiNi合金化学成分更加准确均匀；与石墨坩埚感应熔炼相比,利用BaZrO3坩埚制备的TiNi合金丝材表现出了更为优良的形状记忆回复率和抗疲劳性能,其形状记忆回复率在550℃保温20min淬火后,变形量为2%时能够达到98.62%,其疲劳性能在500℃保温20min后淬火后能够达到3072次。

Abstract:

TiNi shape memory alloy (SMA) is one of the commercially successful shape memory alloys (SMAs) due to its excellent performances. In this work, the 49.3Ti-Ni (at.%) alloy was prepared by vacuum induction melting in 25 kg-grade home-made BaZrO3 crucible, and the cast alloy was turned into wire form (Ф1.0mm). The chemical compositions (including oxygen, nitrogen and carbon) of as-cast alloy were measured and the phase constitution was analyzed by X-ray diffraction (XRD), the microstructures were observed by Optical Microscope (OM) and Scanning Electron Microscope (SEM), the shape memory recovery rate and fatigue life of alloy wires were tested by two home-made test apparatus respectively. Experimental results showed that the contents of oxygen and nitrogen in alloy ingot were 560 ppm and 17 ppm respectively, and the impurities contents in TiNi alloy melted using the BaZrO3 crucible are just eligible to medical devices and surgical implants. The chemical composition melted by the BaZrO3 crucible is more uniform and accurate than by the vacuum arc remelting (VAR). The present presents higher shape memory rate and fatigue life than graphite crucible, the best shape memory recovery can reach 98.62% with 2% deformation and water aging at 550℃ for 20min, and the best average fatigue life can reach 3072 times with water aging at 500℃ for 20min.