Ti51.6Ni43.3Cu4.9Si0.2形狀記憶合金之麻田散體相變態行為與機械性質之研究

Research on Martensitic Transformation Behavior and Mechanical Properties of Ti51.6Ni43.3Cu4.9Si0.2 Shape Memory Alloy

丁宥允(Yu-Yung Ting)

指導教授 ： 陳志軒

國立臺灣大學/工學院/機械工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103258

摘要

本研究利用快速凝固製程(RSP)製作出TiNiCu形狀記憶合金箔帶，並針對其麻田散體相變態行為、顯微結構、形狀記憶效應、以及超彈性進行探討。本研究發現400℃以及500℃的時效條件對Ti50.5Ni44.5Cu5箔帶的相變態溫度影響不大，確認是因為基底成分與噴鑄狀態(as-spun)相同所致。而Ti50.5Ni44.5Cu5箔帶經800℃時效24小時後則因為Ti2(Ni,Cu)以及Ti2(Ni,Cu)3的析出，造成基底成分變化，使得相變態峰值溫度下降。此外，as-spun Ti50.5Ni44.5Cu5箔帶熱循環至1500次後，麻田散體相變態峰值溫度及麻田散體逆變態峰值溫度分別僅下降1.9℃及2.1℃，顯示出良好熱穩定性。在形狀記憶效應實驗中，於170MPa之應力下觀察到as-spun Ti50.5Ni44.5Cu5箔帶具有4.7%之可回復應變，不可回復應變小於0.11%；Ti50.5Ni44.5Cu5箔帶經400℃、500℃時效1小時後則分別有5.1%、5.0%之可回復應變，不可回復應變小於0.11%；800℃時效24小時之Ti50.5Ni44.5Cu5箔帶具有4.7%之可回復應變，不可回復應變約0.17%，從實驗結果可知，Ti50.5Ni44.5Cu5箔帶之可回復應變、不可回復應變會跟材料潛熱以及析出物的狀態有關。從超彈性結果來看，as-spun Ti50.5Ni44.5Cu5箔帶具有4.5%之超彈性，最大彈熱效應的溫度變化量來到10.3℃，而800℃時效24小時後Ti50.5Ni44.5Cu5箔帶在拉伸實驗中僅量測到1%之應變量。經分析結果顯示800℃時效24小時之Ti50.5Ni44.5Cu5箔帶因為太脆而在產生麻田散體變態之前斷裂所致。As-spun Ti50.5Ni44.5Cu5箔帶在經過2%與4%超彈性循環後，試片分別於201、91次循環後破壞，且因4%超彈性循環所累積之差排較多，造成功能性降級較大。最後本研究選用as-spun Ti50.9Ni48.2Si0.2與Ti50.5Ni44.5Cu5箔帶進行超彈性比較。Ti50.9Ni48.2Si0.2箔帶同樣有4.5%之超彈性，最大彈熱效應的溫度變化量為11.3℃。此外，Ti50.9Ni48.2Si0.2箔帶在經過4%超彈性循環後，Ti50.9Ni48.2Si0.2箔帶因為厚度分布較不均，使疲勞壽命較差，但因Ti50.9Ni48.2Si0.2箔帶晶粒尺寸較小，具有細晶強化效果，所產生的功能性降級幅度較小。不同溫度下之超彈性測試顯示Ti50.9Ni48.2Si0.2箔帶可在40~55℃溫度範圍內展現2%超彈性性能；Ti50.5Ni44.5Cu5箔帶可在69~94℃溫度範圍內具有3%超彈性性能。此外，也針對箔帶於不同溫度下之彈熱效應進行量測，並計算出材料性能係數作為固態冷媒選用之依據。

關鍵字

形狀記憶合金箔帶 ； 麻田散體相變態 ； 超彈性 ； 彈熱效應

並列摘要

In this study, the rapid solidification process (RSP) was used to produce TiNiCu shape memory ribbon, and its phase transformation behavior, microstructure, shape memory effect, and superelasticity were investigated. This study revealed that aging treatments at 400°C and 500°C had minor effects on the phase transformation temperatures of Ti50.5Ni44.5Cu5 ribbon. No precipitates were observed in the Ti50.5Ni44.5Cu5 ribbon, and the composition of the matrix remained unchanged after aging at 400°C and 500°C. On the other hand, the Ti50.5Ni44.5Cu5 ribbon aged at 800°C for 24 hours exhibited the precipitation of Ti2(Ni,Cu) and Ti2(Ni,Cu)3, and the composition of matrix changed, resulting in lower transformation temperatures. The thermal cycling test showed that the peak temperature of the martensitic phase transformation and the reverse transformation decreased by 1.9°C and 2.1°C, respectively, after the as-spun Ti50.5Ni44.5Cu5 ribbon was thermally cycled 1500 times, indicating the excellent transformation stability of the ribbon. For the shape memory effect, it was observed that the as-spun Ti50.5Ni44.5Cu5 ribbon showed a reversible strain of 4.7% under a stress of 170 MPa, and the irreversible strain was less than 0.11%. Ti50.5Ni44.5Cu5 ribbon aged at 400℃ and 500℃ for 1 hour manifested reversible strain of 5.1% and 5.0% respectively, and their irreversible strain was less than 0.11%. Ti50.5Ni44.5Cu5 ribbon aged at 800℃ for 24 hours exhibited a smaller reversible strain of 4.7% and a larger irreversible strain of about 0.17%. The results of the shape memory effect showed that the reversible and irreversible strains of the Ti50.5Ni44.5Cu5 ribbon were closely related to the latent heat and the precipitation phenomenon. From the results of the superelasticity test, the as-spun Ti50.5Ni44.5Cu5 ribbon had a superelasticity of 4.5%, and the max elastocaloric temperature drop reached -10.3℃. After aging at 800℃ for 24 hours, Ti50.5Ni44.5Cu5 ribbon only demonstrated 1% strain in the tensile test. This result showed that the Ti50.5Ni44.5Cu5 ribbon aged at 800°C for 24 hours was too brittle due to the large amount of precipitates formed during the treatment. Cyclic superelasticity test of the as-spun Ti50.5Ni44.5Cu5 ribbon was performed with maximum strains of 2% and 4%, and their lifetime were 201 and 91 cycles, respectively. Besides, defects were accumulated during the superelastic cycles, resulting in functional degradation. Finally, superelasticity of as-spun Ti50.9Ni48.2Si0.2 and Ti50.5Ni44.5Cu5 ribbons were compared. The Ti50.9Ni48.2Si0.2 ribbon exhibited a superelastic strain of 4.5%, and the maximum elastocaloric temperature drop of -11.3℃. Experimental results showed that the Ti50.9Ni48.2Si0.2 ribbon exhibited a smaller residual strain due to its finer grain size. Cyclic superelasticity test on Ti50.9Ni48.2Si0.2 ribbon with 4% strain showed that the Ti50.9Ni48.2Si0.2 ribbon had a shorter lifetime of 41 cycles due to uneven thickness distribution. However, the Ti50.9Ni48.2Si0.2 ribbon showed better functional stability during cyclic loading due to its fine grain size. Superelasticity experiments of the ribbons were also carried out at different temperatures, showing that the Ti50.9Ni48.2Si0.2 ribbon exhibited superelasticity of 2% at temperature ranges between 40℃ to 55℃; Ti50.5Ni44.5Cu5 ribbon exhibited superelasticity of 3% at temperature ranges between 69℃ to 94℃. In addition, the elastocaloric effects at different temperatures were also measured. The coefficient of performance of the materials was calculated as an indicator for selecting solid-state refrigeration materials.

並列關鍵字

Shape memory ribbon ； Martensitic transformation ； Superelasticity ； Elastocaloric effect

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