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Title: | 熱循環對不同順序多階麻田散體相變態影響之研究 Effects of Thermal Cycling on Different Sequences of Multi-stage Martensitic Transformation |
Authors: | 王耀智 Yao-Chih Wang |
Advisor: | 薛人愷 Ren-Kae Shiue |
Keyword: | 形狀記憶合金,多階相變態,熱循環,變態溫度,降伏強度,剪應變 s, Shape memory alloy,Multi-stage transformation,Thermal cycling,Transformation temperature,Yield strength,Shear strain (s), |
Publication Year : | 2023 |
Degree: | 碩士 |
Abstract: | 鈦鎳基形狀記憶合金有B2⟷B19’、B2⟷R相、B2⟷B19、B2⟷R相⟷B19’及B2⟷B19 ⟷B19’等不同的多階麻田散體相變態順序,首先我們將先分析Ti50Ni40Cu9Co1及Ti50Ni40Cu8Co2這兩者之二階相變態為B2⟷R相⟷B19’或B2⟷B19 ⟷B19’,研究結果顯示當Co添加量只有1at.%時,Ti50Ni40Cu9Co1會有和Ti50Ni40Cu10相同之B2⟷B19 ⟷B19’二階相變態順序,且由於Co的添加使得麻田散體相變態之變態溫度有大幅度地下降,接著當Co添加量達到2at.%時,Co對Ti50Ni40Cu8Co2合金變態順序之影響已大於Cu之影響,因此Ti50Ni40Cu8Co2具有和Ti50Ni48Co2相同之B2⟷R相⟷B19’二階相變態順序。另一方面,本研究將探討經900℃均質化的Ti50Ni50、三元合金Ti50Ni50-xDx(D=Fe、Pd、Cu)及四元合金Ti50Ni40Cu9Co1、Ti50Ni40Cu8Co2經過50次熱循環後其變態溫度所受之影響。熱循環過程中會有不可逆之差排不斷的累積,所以變態溫度幾乎都會隨著熱循環次數增加而不斷下降,其背後原因和形狀記憶合金本身之降伏強度及不同變態順序在變態過程中產生之剪應變值s等因素有關,實驗結果顯示熱循環對不同相變態順序變態溫度之降低程度和各項變態順序之剪應變值s相同,由大到小都為: B2⟷B19’ > B2⟷B19 > B2⟷R。此外,熱循環對二階相變態其變態溫度降低之影響如同其對一階相變態者,這顯示在二階相變態中這二個相變態間之相互影響並不大。 There are various multi-stage martensitic phase transformation sequences of TiNi-based shape memory alloys, including B2⟷B19', B2⟷R phase, B2⟷B19, B2⟷R phase⟷B19', and B2⟷B19⟷B19'. First, we analyze the second-order phase transformations of Ti50Ni40Cu9Co1 and Ti50Ni40Cu8Co2, specifically B2⟷R phase ⟷ B19' or B2⟷B19⟷B19'. The results show that when the Co content is only 1at.%, Ti50Ni40Cu9Co1 undergoes the B2⟷B19⟷B19' second-order phase transformation sequence as well as Ti50Ni40Cu10. Besides, the addition of Co significantly lowers the transformation temperature of the martensitic phase transformation. On the other hand, when the Co content reaches 2at.%, the influence of Co on the transformation sequence in Ti50Ni40Cu8Co2 becomes more significant than that of Cu. As a result, Ti50Ni40Cu8Co2 exhibits the same B2⟷R phase⟷B19' second-order phase transformation sequence as Ti50Ni48Co2. Furthermore, this study investigates the influence of 50 thermal cyclings on the transformation temperatures of Ti50Ni50 (homogenized at 900℃), ternary alloys Ti50Ni50-xDx (D=Fe, Pd, Cu), and quaternary alloys Ti50Ni40Cu9Co1 and Ti50Ni40Cu8Co2. During the thermal cycling process, irreversible dislocation accumulations occur, resulting in a continuous decrease in the transformation temperatures. The underlying reasons for this phenomenon are related to factors such as the yield strength of the shape memory alloy and the shear strain values (s) generated during the transformation process, which vary with different transformation sequences. The experimental results reveal that the extent of temperature reduction for different transformation sequences during thermal cycling follows the same order as the shear strain values (s): B2⟷B19' > B2⟷B19 > B2⟷R. Additionally, the influence of thermal cycling on second-order phase transformations is similar to that observed in first-order phase transformations, indicating that there is not much mutual influence between these two phase transformations in second-order transformations. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/88595 |
DOI: | 10.6342/NTU202302297 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 材料科學與工程學系 |
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