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標題: | 時效後Ti49.3Ni50.7形狀記憶合金變態特性及記憶性質之研究 Transformation Characteristics and Memory Properties of aged Ti49.3Ni50.7 Shape Memory Alloy |
作者: | Kuo-Hsiang Chang 張國祥 |
指導教授: | 吳錫侃 |
關鍵字: | 富鎳TiNi形狀記憶合金,時效硬化,一階/二階時效,形狀記憶效應,超彈性,應力應變循環,制振能, Ni-rich TiNi shape memory alloys,precipitate hardening,one-step and two step aging,shape memory effect,pseudoelasticity,damping capacity, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 本研究針對Ti49.3Ni50.7 形狀記憶合金(SMA)之形狀記憶效應(SME)、超彈性(PE)與超彈性應力應變循環等性質之提升作一系列的探討。900℃×1hr固溶處理後之Ti49.3Ni50.7 SMA若未經任何時效處理強化者,其硬度值較低,且PE性質由於SIM逆變態較少而使得殘留應變較多,SME之可回復應變較小,其超彈性應力應變循環性質也較差。固溶處理後之Ti49.3Ni50.7 SMA經時效後會有Ti3Ni4之析出硬化,本研究將時效時溫度保持一致者稱為一階段時效,而先在低溫時效後再高溫時效者稱為二階段時效。研究結果發現,一階段300℃時效者在50小時可達347HV之最大硬度,此硬度值也較其他一階段時效者大,且具有良好的PE、SME與超彈性應力應變循環性能。在二階段時效者中,先250℃時效再300℃時效者,其最大硬度值可達333Hv,雖然不及一階段300℃時效者,但卻能有效提升σM及σR值,使其儲存能量較大,儲能效率也是最高的,因此有優異的PE性能,而其SME之性能也幾乎達100%。在制振能的研究方面,發現二階段時效者若其高溫時效為300℃者相變態時之tanδ值相當高並有相當明顯的storage modulus極低值,顯示其擁有良好的制振能。在二階段時效下若其高溫時效為300℃或400℃並使時效硬度達到最大值時,400℃時效者之PE性質的σM及σR值都較300℃者來的低,儲存能量及儲能效率也較差。研究結果顯示,一階段時效或兩階段時效並使時效硬度達到最大值時,其SME表現差不多,應變量幾乎都可完全回復;雖然一階段時效者最高硬度較大,也可在較短的時效時間下達到最大硬度,但兩階段時效者在最高硬度下其PE的各項特性上都較一階段時效者來的高,且兩階段時效者也可提升相變態時之制振能,顯示兩階段時效者較有利於強化PE、SME與超彈性應力應變循環等性能。 In this study, the optimal properties of shape memory effect (SME), pseudoelasticity (PE), damping capacity (DC) and PE stress-strain (σ-ε) cycling of Ti49.3Ni50.7 shape memory alloy (SMA) are investigated. The solution-treated (900℃×1h) Ti49.3Ni50.7 SMA without aging has the worst properties, as compared with the aged one. One-step and two step aging treatments are conducted in the temperature range between 250℃ and 450℃ for different aging time and Ti3Ni4 precipitates are formed and the hardness increases due to precipitation hardening. Experimental results show that one-step aging heat-treated at 300℃×50h would attain the maximum specimen’s hardness 347Hv and have rather good PE, SME and PE σ-ε cycling properties. In two-step aging, specimen pre-aged at 250℃×1h and then aged at 300℃×50h can obtain the maximum hardness 333Hv. Though the maximum hardness obtained by two-step aging is less than that by one-step aging, two-step aged specimen can effectively enhance σM and σR values to increase the stored energy during PE σ-ε cycling and thus exhibit excellent PE performance. The DC tests indicate that the two-step aged specimen has relatively high tanδ and conspicuous minimum storage modulus during martensitic transformation. Both one-step and two-step aged specimens which have maximum hardness are almost fully recovered strain in SME tests. Besides, the one-step aged specimen can attain higher hardness value with less heat-treating time, but the overall SME/PE properties of two-step aged one are better. This infers that two-step aging is benefit to improve the properties of PE, SME, PEσ-ε cycling and damping capacity. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/23785 |
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顯示於系所單位: | 材料科學與工程學系 |
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