鈮、矽添加對銅鋁鈹合金之相變態與高溫形狀記憶效應的影響

Effects of Nb, Si additions on the Cu-Al-Be Alloys' phase transformation anad high temperature SME

蔡彥明(Yan-Min Tsai)

指導教授 ： 王文雄

共同指導教授 ： 徐永富

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01010

摘要

本實驗以真空石英管熔配Cu-11.55wt.% Al-Be形狀記憶合金，所得鑄錠經均質化後切成三等分，接著利用VAR將其中兩塊添加少量鈮、矽元素後再進行熱軋。試片於850℃淬火至冷水中，然後進行冷加工、拉伸、300℃時效、熱循環等實驗，最後以DSC變態溫度量測、形狀回復率測試、硬度試驗、X光繞射分析以及OM、SEM、TEM之顯微組織觀察，來探討殘留相對Cu-Al-Be合金之高溫形狀記憶效應與相變化的影響。
實驗結果顯示，高溫Cu-Al-Be合金在固溶-水淬後有麻田散體穩定化現象發生，必須藉由再序化處理才具有形狀記憶效應。添加少量鈮、矽後會在Cu-Al-Be基地上形成殘留相，其可抑制麻田散體成長而促進晶粒細化，使機械性質及形狀回復率都有些微提升。至於超彈性拉伸試驗的結果顯示，Af變態溫度較高的合金，在250℃高溫具有較好的形狀回復能力。此外各合金於時效後，基地上主要析出物為α1-plate及少量γ2(Cu9Al4)析出物，且殘留相於時效期間亦會有成長、偏析的現象，導致高溫形狀記憶效應逐漸劣化。由X光繞射分析可知麻田散體與α1-plate皆為M18R結構，而γ2為D83結構。最後由TEM觀察證明，熱循環100次後形狀回復率下降，是由於差排的產生。

關鍵字

形狀回復率 ； 形狀記憶效應 ； 超彈性拉伸

並列摘要

In this experiment, the Cu-11.55wt% Al-0.32wt% Be shape memory alloy was firstly melted at 1100℃ in a evacuated quartz capsule. After homogenization, the ingot was cut into three equal parts, and two of them were added small amount of Nb and Si by VAR. After hot rolled, the specimen were quenched into water from 850℃ and aged at 300℃.The characteristics of these specimens were investigated by DSC, tension test, thermal cycling test and shape memory recovery tests. The microstructure and crystal structure of aged specimens were analyzed by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD).The purpose of present study is to discuss the influence of Nb and Si addition on the shape memory recovery and phase transformation of Cu-11.55wt%Al-0.32wt%Be alloy.
The results show that the three alloys have stabilization phenomenon after solution treatments and they must be performed with the reordering treatment in order to obtain shape memory effect. However, Nb and Si additions will induce the residual phases formed in the matrix, it can restrain the growth of martensite and contribute to fine grains that improve mechanical and shape recovery properties. The superelastic test shows that the alloy with higher reverse transformation temperature (Af), the better it’s shape recovery ability at 250℃. Besides, the main precipitates of each alloy after aging are α1-plate and a few γ2(Cu9Al4). Moreover, the residual phases have growth and segregation phenomenons during aging, so it causes the gradual degredation of high temperature shape memory effect. TEM and X-Ray diffraction analysis show that martensite and α1-plate are M18R structure and γ2 is D83 structure. Finally, TEM results prove that the reduce of shape recovery ability is due to the present of dislocations after 100th thermal cycling.

並列關鍵字

shape memory recovery ； shape memory effect ； superelastic test

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