| 摘要: | 金屬玻璃有高硬度、高強度、高楊氏模數與高彈性形變能力，也有良好的耐腐蝕性與耐磨耗性，但其在室溫條件下卻沒有延性，幾乎沒有塑性行為，根據文獻所提出的解決方式，將材料製成複合材料，能有效提升其塑性行為，材料才有更廣的應用範圍。
我們想要探討材料在形變過程中延展性的機制，有學者提出材料內部的枝晶(dendrite)的大小與枝晶間距離能有效影響剪切帶(shear band)的擴張與集中，在材料介面(晶相與非晶相的接面)，也有學者利用模擬的方式佐證介面能有效的吸收應變能，但是材料內部的晶體，尚未有明確的解釋機制，本篇論文藉由不同的實驗，觀察材料在受力時其晶體微觀結構變化，去分析其影響的機制。
本實驗先由熱差分析儀量(DSC)，分析不同形變程度，對熱性質的影響，說明內部結構的變化。接著用高能量X光繞射對材料量測，得到半高寬(FWHM)資訊。並藉由材料不同壓縮循環時半高寬變化，並對照Convolutional Multiple Whole Profile fitting (CMWP)所獲的微結構資訊，來解釋此現象。再利用高解析掃描穿透式電子顯微鏡影像(HR-TEM)、與分子動力模擬(Molecular dynamics)佐證我們建構的模型與解釋機制之正確性，進而了解影響材料內部晶體延展性的機制。
;Metallic glass has plenty of advantages, including high hardness, strength, Young’s modulus, elasticity, and good corrosion and wear resistance. However, it becomes brittle under room temperature and nearly does not perform plastic deformation. Hence, introducing the crystal materials into composites can enhance the plasticity in order to provide a wider variety of applications.
To understand how to enhance the ductility of the material, some scholars have proposed that the size of the interior dendrites and the distance between each dendrite can affect the expansion and concentration of shear band, and some scholars have proved that the material interface, where the boundary between crystalline and amorphous phase meet, can absorb strain energy effectively by simulations. Although the above ideas have been proved, there is no clear explanation for the interior dendrites of materials. By observing the changes in microstructure of dendrites under stress in different experiments, we can analyze the effects caused by the changes.
To explain the changes in interior structure of material, the first experiment will be conducted to analyze the different levels of deformation and effects to heat by Differentiation Scanning Calorimetry (DSC). Next, High-energy X-ray Diffraction will be used to obtain the information of Full Width Half Maximum (FWHM). By means of changes of FWHM under different compression cycles, the phenomenon can be explained with the aid of comparisons of microstructure information by Convolutional Multiple Whole Profile fitting (CMWP). Then using of High Resolution Transmission Electronic Microscopy (HR-TEM) and Molecular dynamics, we can prove the accuracy of our built model and the explanations for the above mentioned phenomenon, therefore we can have a better understanding on mechanism of improving the ductility of the bulk metallic glass composite materials. |
