Ti50-XNi15Pd25Cu10Vx(x=0~10)與Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15
形狀記憶合金之麻田散體相變態行為與機械性質研究

本研究之第一部分由TiNiPdCu 合金出發，設計TiNiPdCuV 系列之合金。加入V 取代Ti，使V的比例逐漸增加，分別為Ti50-xNi15Pd25Cu10Vx(x=0、0.5、1、1.5、2、2.5、3 和10)八種合金。研究不同比例之V對合金的形狀記憶效應、變態溫度、抗熱循環疲勞強度、顯微結構、析出強化的影響和晶體結構的變化，以及時效處理過後V 的比例對其形狀記憶性能的影響。在TiNiPdCu 合金中加入V 會影響合金的相組成，隨著V 的比例增加，合金會從兩相組成(類TiPd、類Ti2Ni)轉變成三相組成(類TiPd、類Ti2Ni、TiPdCu)在轉變成四相組成(類TiPd、類Ti2Ni、TiPdCu、V)。在TiNiPdCu 合金中加入V 也會降低合金的變態溫度，含V 量高的合金變態溫度低且強化析出效果的能力越好。在TiNiPdCu 合金中加入適量的V 會增強合金熱循環穩定性，且能夠保有良好的形狀記憶效應、超彈性以及彈熱效應。本研究之第二部分則是高熵形狀記憶合金Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15，透過控制熱處理溫度與時間調整形狀記憶效應和機械性質。研究不同時間的時效處理對合金的形狀記憶效應、變態溫度、抗熱循環疲勞強度以及析出強化的影響。時效處理過的Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15 合金會有兩階變態(低溫變態TL及高溫變態TH)的特性，且兩階變態的變態溫度皆會隨著時效時間增加而上升。其中TH 會隨著時效時間增加而被抑制轉變為只能透過應力誘發的麻田散體變態，展現出類似應變玻璃的特性。可於DSC 中量測到的TL 變態的熱循環穩定性並未隨著時效時間增長及析出硬化效果而有明顯改善，本研究顯示Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15 高熵形狀記憶合金具有許多特殊但未知的性質，如形狀記憶效應測試時，TH 會在TL 的應變飽和後才能被誘發等特性，以及多次熱循環後TL漸消而TH漸長之現象。顯示高熵形狀記憶合金領域仍有許多未明且值得探討的特殊性能。

關鍵字

形狀記憶合金；高熵合金；時效熱處理；熱循環；形狀記憶效應；超彈性；彈熱效應

並列摘要

The first part of this research investigated TiNiPdCuV series alloys based on TiNiPdCu SMA. V was added into TiNiPdCu alloy to replace Ti. 8 alloys withcompositions of Ti50-xNi15Pd25Cu10Vx(x=0、0.5、1、1.5、2、2.5、3 and 10) were prepared. The effect of the amount of V on martensite transformation temperature, thermal cycle stability, microstructure, precipitation strengthening, lattice constants. Additional of V into TiNiPdCu alloy changed the phase constitution of the alloy. The phase constitution changed from two phases (TiPd-like matrix and Ti2Ni-like second phase) to three phases (TiPd-like, Ti2Ni-like and TiPdCu), and finally became four phases (TiPd-like, Ti2Ni-like, TiPdC, and V-rich). The addition of V into TiNiPdCu alloy also decreased the martensite transformation temperature. The higher the amount of V in the alloy, the higher the precipitation strengthening effect and the lower the martensite transformation temperature. Adding 1.5 at.% of V improved the thermal cycle stability of the alloy. At the same time, it maintained good shape memory effect, pseudoelasticity, and elastocaloric effect. The second part of this research focused on the Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15 high entropy SMA. The effects of aging treatment on shape memory effect, martensite transformation temperature, thermal cycle stability, and the precipitation strengthening effect are investigated. Two martensitic transformation phenomena were obaserved when the aging time was within 1 h. The transformation at the higher temperature, TH, was suppressed and could only be induced by stress during the aging treatment. The thermal stability of the transformation at the lower temperature, TL, was not obviously improved after precipitation strengthening. It was also noted that Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15 high entropy SMA exhibited many unknow but special properties, such as strain-glass-like two-stage and thermal-cycling-enhanced transformation behaviors, which means that high entropy SMA is a new field that worth further studies.

並列關鍵字

shape memory alloy ； high entropy alloy ； aging process ； thermal cycle ； shape memory effect ； psuedoelasticity ； elastocaloric effect

參考文獻

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Ti50-XNi15Pd25Cu10Vx(x=0~10)與Ti16.5Zr16.5Hf16.5Ni30.5Co5Cu15 形狀記憶合金之麻田散體相變態行為與機械性質研究

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