本文以分子動力學研究Ni-Ti合金塊材之形狀記憶特性，觀察不同Ni含量比例、不同原子分布與不同晶格排列方向的情況下對相轉變的影響，並在低溫時施予不同的複合加載至塑性變形，再進行升降溫循環以檢測任意加載所造成的塑性變形是否皆可經溫度循環而回復原狀。
由模擬結果得知Ni-Ti合金在高溫時以體心立方結構(沃斯田體相)穩定存在，在低溫時，Ni比例不為50%的合金皆轉變為斜方體結構(麻田散體相)，相變溫度隨著Ni含量增加而提高。此外，對於Ni含量為53%的合金而言，其相轉變溫度不受其內部原子分布位置與晶格排列方向所影響。
由模擬結果得知，在低溫下Ni-Ti合金並非施予任意加載至塑性變形後皆具有形狀記憶特性，以CNP參數法分析可發現唯有施加能造成內部雙晶方向層於特定平面上移動的加載才能透過溫度循環使合金回復原狀。在最大剪應力理論中，觀察到具有形狀記憶特性的模擬其最大剪應力值較其餘無法回復原狀者小。透過滑移向量輔助可得知施予使內部原子產生差排的加載方式不具有形狀記憶效應。

We employed molecular dynamics simulation to investigate the shape memory properties of Ni-Ti alloy bulks. The effects of Ni composition ratio and the simulated crystal orientation on phase transformation were studied. At low temperature, different loading conditions were applied to the alloy bulk till plasticity took place. Then the deformed models went through the temperature cycle without loadings to examine whether it would restore to its original shape or not.
Form the simulation, we found the Ni-Ti alloy is body-centered cubic structure (austenite phase) at high temperature and transforms to monoclinic structure (martensite phase) at certain temperature, except for the 50% Ni composition ratio. The phase transformation temperature was affected by the Ni composition ratio. It was observed that the simulated models with different Ni atomic distribution and crystal orientations would have the same phase transformation temperature.
For different loading simulations, it was found that not every plastic deformed model would restore to its original shape after the thermal cycle. Combined with common neighbor parameter observation, it was noticed that only those were able to force the twinning variants to move on the specific plane would exhibit shape memory behavior. For those loadings which would restore to its original shape, the corresponding maximum shear stress was clearly smaller than those that did not restore. With the assist of slip vector, it was known that the model which had dislocation would not have shape memory properties.

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