請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/18044
標題: | TiNi基形狀記憶合金之制震能與時效初期性質演變之研究 Studies on Damping Capacities and Properties Evolution of Early-Aged TiNi-based Shape Memory Alloys |
作者: | Chen Chien 簡甄 |
指導教授: | 吳錫侃 |
關鍵字: | TiNi形狀記憶合金,制震能,麻田散體變態,應變/頻率掃描,小角度X光散射,熱物理性質, TiNi shape memory alloys,damping properties,martensitic transformation,strain/frequency sweep,small X-ray scattering,strain glass, |
出版年 : | 2015 |
學位: | 博士 |
摘要: | 本研究利用動態機械分析儀(DMA)探討Ti50Ni50−xCux (x = 0~30 at.%) 及Ti50Ni50−xFex (x = 1~4 at.%)形狀記憶合金(SMA)在溫度、應變與頻率掃描下之制震能。實驗結果顯示Ti50Ni50−xCux在B2→B19變態時,因其雙晶邊界活動力較高,所以比在B2→B19’變態會有較高之制震能與較大的儲存模數軟化。在應變掃描下,Ti50Ni50−xCux之tan δ值會隨著應變量的增加而增加,隨著頻率的上升而減少,使用tan δ = K εn公式回歸後,求出n=0.41-0.60,較為符合磨擦形式模型(n=0.5)。此外,氫原子對Ti50Ni50−xFex在R→B19’的貢獻大於在B2→R的貢獻,這是由於R相及B19’相都有大量的雙晶邊界可以和氫原子交互作用使制震能上升。而在持溫條件下,Ti50Ni50−xFex 在R→B19’變態的本質制震能比B2→R者高也是因為前者的雙晶邊界較多。本研究同時使用小角度X光散射儀(SAXS)分析Ti48.7Ni51.3 SMA在250oC 時效初期之奈米域演變,其二維圖顯示此奈米域為圓盤狀且為不均勻分布。由一維SAXS曲線可以計算出奈米域的半徑及厚度,且隨著時效時間之增加至3小時前,奈米域僅有厚度之成長。藉由量測時效初期之Ti48.7Ni51.3 SMA的熱物理性質,可以發現其有應變玻璃之特徵,即電阻會隨溫度上升而下降,但熱導與席貝克係數卻隨溫度上升而上升,並顯示出其玻璃轉脆溫度會隨著時效時間之增加而往高溫移動。 Damping properties of Ti50Ni50−xCux (x = 0~30 at.%) and Ti50Ni50−xFex (x = 1~4 at.%) shape memory alloys (SMAs) are characterized under temperature, strain and frequency sweep tests by dynamic mechanical analyzer. Experimental results indicate that, for Ti50Ni50−xCux SMAs, the magnitudes of tan δ value and storage modulus (E0) softening/hardening exhibited in B2↔B19 transformation are all higher than those in B2↔B19’ one. It is suggested that the greater mobility of the twin boundaries and the larger magnitude of the strain variation are both to cause the higher tan δ value. In addition, the relaxation peaks are observed in B19’ martensite, but not in B19 martensite, because the latter has intrinsically rare twinned variants. In the strain sweep test, the tan δ value decreases as the frequency increases, but it increases as the applied strain increases. The tan δ curves of the strain sweep tests in Ti50Ni50-xCux SMAs (x=0~20 at.%) can be fitted by tan δ = K εn with n values of 0.41-0.60 which are close to the friction type model (n=0.5). For Ti50Ni50−xFex SMAs, the internal friction (IF) contribution of hydrogen atoms at R→B19’ transformation is more than that at B2→R one because the former has abundant twin boundaries in both R-phase and B19’ martensite, which can interact with the hydrogen atoms to dissipate energy. The tan δ values of (IFPT+IFI)R→B19’ are higher than those of (IFPT+IFI)B2→R peak. This feature comes from the facts that the twin boundaries of R→B19’ transformation is more than those of the B2→R one. By the SAXS technique, the nanodomain evolution corresponding to strain glass in quenched and 250oC early-aged Ti48.7Ni51.3 SMA can be revealed. The 2D SAXS patterns provide the direct evidence that the shape of strain glass nanodomains is plate-/disk-like, and these nanodomains lie on the habit lattice planes. The nanodomains are nucleated heterogeneously in different grains, and the model analysis of 1D SAXS profiles quantitatively determines the strain glass nanodomains’ radii and thicknesses which the thickness of 3hr aged specimen are larger than that of as-quenched one. The results of thermal physical properties indicate that the ρ decreases but the ? and S increase as the temperature increases which demonstrate the characteristics of the strain glass exhibited in 250oC early aged Ti48.7Ni51.3 SMA. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/18044 |
全文授權: | 未授權 |
顯示於系所單位: | 材料科學與工程學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-104-1.pdf 目前未授權公開取用 | 11.19 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。