以分子動力學法分析非晶質鋯銅合金薄膜之機械性質與成形特性

Mechanical properties and forming mechainism of ZrCu amorphous nanofilms using molecular dynamics simulations

侯鈞仁(Chun-Jen Hou)

指導教授 ： 吳政達

中原大學/工學院/機械工程研究所/碩士(2017年)

https://doi.org/10.6840/cycu201700709

摘要

本文利用分子動力學法分析非晶質鋯銅合金薄膜在奈米尺度下之機械性質與成形特性。研究中發現非晶材料受力形成剪切帶前，原子因受剪切力影響，部分區域形成剪切轉換區，並逐漸結合成剪切帶，而此材料受力時剪應變會呈現均勻狀的分佈。在壓縮模型中發現當溫度升高時，所需的壓縮應力會增加；但在拉伸模型中拉伸應力則是會隨著溫度的上升而下降。另外研究中也發現非晶結構在超過玻璃轉化溫度後其延展性會增加。在達到玻璃轉換溫度後材料會轉變成黏彈體。在速度效應模擬試驗中發現當拉伸速度越快時，所需的應力也會越高；壓縮也一樣，速度越大，需要的應力也越大。但當拉伸速度到達200 m/s時，其所需的拉伸應力會比150 m/s還要低一些。原子的能量會依拉伸速度上升而增加，一樣當拉伸速度為200 m/s時，原子的能量會下降。在壓印模擬試驗中發現，模具下壓快接觸到材料時，會有原子吸附的現象。模具接觸到材料時，剪應變會先集中在模具邊角的位置，且溫度越低，所需的壓印力會越大，而當溫度升高至玻璃轉化溫度時，所需之力會大幅的減少。從流場圖可看出當溫度較低時，材料中下段的原子幾乎沒有位移，而隨著材料因溫度升高而軟化，會使得剪應變容易延伸至材料底部。在模具壓印回彈率曲線圖可以看出在材料凹痕和凸起的寬度的部分，回彈率會隨著溫度升高而升高，但在高度部分則較無規律性。

關鍵字

分子動力學 ； 非晶質合金 ； 拉伸壓縮模擬試驗 ； 奈米壓印

並列摘要

This study investigates mechanical properties and formings mechainism of ZrCu nanofilms using molecular dynamics simulations. The study found that shear transformation zones form due to action of shear stress and they gradually combined into a shear band with increasing shear stress. When the material under loading, the shear strain will exhibit a uniform shape distribution. It found that when temperature was rising in the compression model, the required compressive stress will increase; but in the stretch model, tensile stress will decrease with increasing temperature. And also found that amorphous structure was found in more than the glass transition temperature of the material will be transformed into a viscoelastic body. In the velocity effect test of tensile model, found that when the velocity of tensile was faster, the required stress will be higher. As the same as effect in the compression model, when the tensile velocity was faster, the required compression stress will be higher. But when the tensile rate reaches 200 m/s, the required tensile stress is lower than 150 m/s. The energy of the atom increases as the velocity of tensile increases, when the tensile velocity is 200 m/s, the energy of the atom will decrease. In the nanoimprinting simulation test, found that when the mold almost touch the material, there will be the phenomenon of atomic adsorption. When the mold comes into contact with the material, shear strain will first focus on the position of the mold corner. And have the biggest imprint force required when the lower the temperature. When the temperature rises to the glass transition temperature, the required force will be greatly reduced. From the flow field diagram can be seen when the temperature was lower, there is no displacement of the atom in the lower part of the material, as the material softens because high temperature, it makes the shear strain easy to extend to the bottom of the material.

並列關鍵字

molecular dynamics ； amorphous alloy ； tensile and compression simulation ； nanoimprinting

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