菱方晶系形狀記憶合金之微結構分類與分析研究

Abstract

菱方晶系形狀記憶合金在工業或生醫領域應用上具有很大的潛力，例如制動器或感測器。大部分有關菱方晶系之微結構的研究，通常都注重在典型魚骨頭圖形之結構。然而還有其他有趣的圖形尚未被討論，如非典型魚骨頭、牙刷狀圖形與棋盤狀圖形。本研究利用幾何線性相容理論發展出一套新的計算模型，尋找所有可能的二階板層雙晶結構，並將它們分類成七種結構家族。此外，更配合自行研發的微結構自動辨識系統與實驗互相驗證，模擬結果與實驗相當吻合。本模型在計算上十分有效率且快速，可以即時的推測出試片內部三維的立體結構。接著，再使用非線性相容理論，將七種結構家族的非相容性加以分析。結果顯示結構的非相容性與其在實驗中被發現的機率相關。不僅如此，我們更製作出多個結構家族的三維立體單位晶胞排列，分析微結構內部的受力狀況，以說明實驗中觀察到的現象。

The trigonal shape memory alloys (SMAs) have a great potential to be utilized as the applications with special purposes, such as actuators with high operation frequency. Most studies on the trigonal microstructures typically focus on the well-known classic herringbone pattern, but many other patterns are also possible, such as non-classic herringbone, toothbrush and checkerboard patterns. In the current work, a systematic procedure is developed to find all possible laminate twin microstructures by using geometrically linear compatibility theory and classify them as seven families of twin pattern. The procedure is verified by SEM images with the information of crystallographic axes of unitcells obtained by EBSD, showing good agreement. The current procedure is rapid, computationally efficient and sufficiently which can analyze the microstructure of specimen immediately. Many interesting trigonal R-phase patterns are found in the specimen. Then, their incompatibility are analyzed with nonlinear compatibility theory. The relationship between such incompatibility and the likelihood of occurrence of the microstructures is revealed. Moreover, 3-dimensional unit cell alignment of the patterns is illustrated to explain the phenomenon of observations.