富鈦 (Ti>51.5 at.%) 鈦鎳形狀記憶合金箔帶相變態行為及性能研究

Transformation Behaviors and Properties of Ti-rich (Ti > 51.5 at%) TiNi Shape Memory Alloys Ribbons

王嚴徵(Yen-Cheng Wang)

指導教授 ： 吳錫侃

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601078

摘要

本研究使用快速凝固製程(RSP)製備2000rpm Ti51.9Ni48Si0.1與Ti52.6Ni46.8Si0.6 SMA 箔帶(Ribbon)，並分析其於as-spun狀態與經500℃時效後之相變態行為、析出行為、顯微結構以及機械性能等。兩成分之箔帶於as-spun狀態皆為完全結晶的狀態，且基地中已有部分奈米級Ti2Ni析出物，由於兩成分之箔帶皆含有RSP製程時摻入的Si，因此經過時效處理後，基地將產生數目更多或尺寸較大的Ti2Ni，使基地逐漸轉為富鎳，進而產生Ti3Ni4析出物，並誘發B2↔R↔B19’的相變態發生。經過DSC、XRD與TEM的分析後，得知Ti51.9Ni48Si0.1基地經時效處理後有兩階段的Ti3Ni4析出行為；而Ti52.6Ni46.8Si0.6經時效後，Ti2Ni與Ti3Ni4兩者先後於不同時效時間產生較明顯的析出行為；隨著時效時間持續增長，Ti51.9Ni48Si0.1箔帶基地中的Ti3Ni4會於500℃時效54hrs以上時逐漸喪失其與基地之整合性應力場，而Ti52.6Ni46.8Si0.6箔帶於時效336hrs時仍無法觀察到此現象。Ti2Ni與Ti3Ni4除了影響箔帶的相變態行為之外，也會對基地產生析出硬化的效果，使Ti51.9Ni48Si0.1與Ti52.6Ni46.8Si0.6箔帶的硬度值提升，並改善其超彈性回復率與形狀記憶效應。本研究顯示Ti51.9Ni48Si0.1箔帶於500℃時效5hrs，硬度值可達3.86GPa，超彈性回復率及應變回復率皆大於90%；而Ti52.6Ni46.8Si0.6箔帶於500℃時效3hrs時，硬度值可達3.48GPa，超彈性回復率大於90%，應變回復率大於97%。因此可得知Ti51.9Ni48Si0.1與Ti52.6Ni46.8Si0.6箔帶兩者經過500℃短時間時效後，可以得到最佳的機械性能。

關鍵字

富鈦形狀記憶合金 ； Ti2Ni與Ti3Ni4析出物 ； 快速凝固製程 ； 相變態 ； 奈米壓痕試驗

並列摘要

Ti51.9Ni48Si0.1 and Ti52.6Ni46.8Si0.6 SMAs’ ribbons prepared by rapid solidification process(RSP) are aged at 500℃ for different times to investigate their transformation sequence, microstructure, precipitation behavior, mechanical properties, etc. As-spun ribbons have fine grains at the contact side and cylindrical grains at the free side with lots of Ti2Ni precipitation(ppts) exsisting at grain boundaries. Compared to ribbons containing less Ti content (Ti <51.5 at.%), Ti51.9Ni48Si0.1 and Ti52.6Ni46.8Si0.6 ribbons require longer aging time to make Ti-rich matrix turn into Ni-rich one due to the precipitation and growth of nanoscale Ti2Ni ppts enhanced by the existence of slight Si content in ribbons. Afterward, Ti3Ni4 ppts will precipitate, which can induce more B2-->R transformation and generate the precipitation hardening effect. The precipitation behavior of Ti2Ni and Ti3Ni4 ppts are confirmed by the potential △H value of DSC tests and the ppts peaks’ intensity of XRD tests. These ppts are also found to affect the ribbons’ phase transformation behavior and mechanical properties. For Ti51.9Ni48Si0.1 ribbons, the precipitation hardening of Ti3Ni4 ppts significantly appears when the ribbons aged at 500℃ for 5hrs and 54hrs, and thus can exhibit higher hardness, better pseudoelasticity(PE)/shape memory effect(SME), as revealed by nanoindentation and dynamic mechanical analysis(DMA) tests. For Ti52.6Ni46.8Si0.6 ribbons, the precipitation hardening induced by both Ti2Ni and Ti3Ni4 ppts appears when the ribbons are 500℃-aged at 3hrs and at the time longer than 10hrs individually, in which the ribbons aged at 500℃ for 3hrs possess the better mechanical properties.

並列關鍵字

Ti-rich shape memory ribbons ； Precipitates ； Rapid solidification process ； Phase transformation ； Nanoindentation ； DMA

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