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鋯銅基金屬玻璃之潛變鬆弛與界面控制變形行為

Time-dependent and interface-controlled deformation behavior of Zr-Cu metallic glasses

作者:陳盈翰
畢業學校:國立中山大學
出版單位:國立中山大學
核准日期:2016-01-14
類型:Electronic Thesis or Dissertation
權限:Copyright information available at source archive--National Sun Yat-sen University....

中文摘要

在本論文中,利用奈米壓痕技術去探討殘留應力對於塊狀金屬玻璃潛變之影響,為了在塊狀金屬玻璃中產生殘留應力,所使用的方法是將塊狀金屬玻璃彎曲限制在金屬圈中,而被彎曲的塊狀金屬玻璃試片其上半部就會存在張應力而下半部就會存在壓應力,經過奈米壓痕潛變測試後可得知,在張應力存在部分其潛變應變速率會明顯大於壓應力的部分,此現象可經由殘留應力對試片結構影響來解釋。
研究也針對鋯銅非晶薄膜、鋯奈米晶薄膜和鋯銅/鋯多層膜進行奈米壓痕潛變的研究,在研究中發現了潛變速率會因為施加應力的改變而發生了交叉現象,跟鋯銅非晶薄膜比起來鋯奈米晶薄膜擁有較高的應力靈敏度,這是因為鋯奈米晶薄膜擁有差排在不同滑移系統下的變形機制和晶界滑移的變形機制,而相對於單層薄膜,鋯銅/鋯多層膜表現出較高的潛變應變速率這是因為眾多界面的貢獻所造成。
最後,利用物理濺鍍製備鋯銅非晶薄膜/鋯奈米晶薄膜的多層膜試片(每層500 nm厚),並且利用聚焦離子束去加工製備出擁有傾斜界面的奈米柱,這些傾斜界面奈米柱可以去探討壓縮應力方向與界面之間在不同的角度關係下的現象,實驗的結果與分子動力學的模擬和Tsai-Hill模型去針對楊氏模數和降伏應力做比較,可得知鋯銅非晶薄膜/鋯奈米晶薄膜的界面剪切模數和界面強度分別是25 GPa和1.0 GPa,透過分子動力學的模擬可了解奈米柱在彈性-塑性的變形現象和模式,實驗的結果與模擬的計算結果相當吻合。
關鍵字:金屬玻璃、多層膜、機械性質、潛變、界面

英文摘要

In this research, the effect of residual stresses on the time-dependent deformation of a bulk metallic glass is investigated by the nanoindentation technique. In order to induce residual stresses, a beam sample was elastically bent and constrained in a steel ring. The upper side of the beam experiences the tensile residual stress, the lower side the compressive residual stress, and the central line nearly nil stress. Afterward, nanoindentation creep tests are performed on this stressed sample at room temperature. The creep rate is apparently higher on the tensile side, and remains lower and nearly fixed on the compressive side. The behavior can be explained by the joint influence of the residual stress and indention loading.
We also attempt to investigate the nanoindentaion time-dependent relaxation tests were performed on the amorphous ZrCu, nanocrystalline Zr and multilayer ZrCu/Zr thin films aiming to explore the different time-dependent behaviors of these materials under the similar load level at room temperature. There appears an interesting crossing phenomenon of the creep rate as a function of applied stress. In comparison with the ZrCu thin films, the Zr film shows higher load/stress sensitivity for the creep response, suggesting the operating of dislocation creep along various slip systems and some minor grain-boundary-sliding creep mechanism. Multilayered ZrCu/Zr thin films also exhibit higher creep response due to the presence of numerous interfaces.
Eventually, an amorphous-ZrCu/crystalline-Zr nanolaminate (500 nm each layer) was initially synthesized using sputter deposition and, then, fabricated into micropillar samples using focus ion beam machining with the amorphous-crystalline (a-c) interfaces inclined to the pillar axis. These pillars were, subsequently, tested in compression in order to study the response of a-c interfaces to the applied shear stress, and further compared with the one that tested with their a-c interfaces normal to the compressive direction. Comparison was made on the experimental, MD and Tsai-Hill data on modulus and yield strength as a function of the angle φ with respect to the loading axis. The extracted interface shear modulus and interface strength for the current ZrCu/Zr is about 25 GPa and 1.0 GPa, respectively. Molecular dynamic simulations are also carried out to reveal the elastic-plastic behavior and, in particular, the deformation mode, of the pillars. The computed results are in excellent agreement with the experimental observations.
Keywords: Metallic glasses, Multilayer, Mechanical properties, Creep, Interface


召集委員 - 鄭憲清

委員 - 林鉉凱

委員 - 朱訓鵬

委員 - 潘正堂

委員 - 林哲信

指導教授 - 黃志青


 

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