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標題: | 以差排密度之強化晶體塑性模型分析鋁合金之析出硬化 Dislocation Density Enhanced Crystal Plasticity Model for Precipitation Hardening of Aluminum Alloys |
作者: | Yi-Liang Cheng 鄭翊良 |
指導教授: | 陳俊杉(Chuin-Shan Chen) |
關鍵字: | 溫變形,晶體塑性有限元素模型,鋁合金,析出物, CPFEM,auminum alloys,precipitates,geometrically necessary dislocation, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本論文目的為建立一創新的計算架構,透過幾何必要差排密度來模擬Al-Mg-Si合金中,因為熱處理製程產生MgSi組成之析出物而導致的析出硬化效應。近年來,輕量化材料的開發為新世代汽車產業發展電動車之重要議題,故高強度輕金屬鋁合金成為了極具開發潛力的關鍵材料。然而,目前尚未有全面性的研究從微觀的角度來探討這些強化機制的影響。 Al-Mg-Si合金的強化機制主要源自於析出物與差排間的交互作用。因此,本研究發展了一套基於差排密度的晶體塑性有限元素模型(CPFEM),用以描述Al-Mg-Si合金中因析出物而發生的強化機制。本研究亦透過TEM影像觀察微觀物理機制,並從中獲取各種時效條件下的材料模擬參數進行模擬。模擬結果顯示,透過分析TEM影像計算獲得的模擬參數,能在晶體塑性模型中有效地描述各時效條件下差排密度的增長,並準確預測不同變形溫度下其降伏強度與極限抗拉強度。 本研究亦使用不確定性量化方法分析TEM影像中析出物之幾何參數,藉由多次取樣來取得多組應力應變資料,並計算其平均值與標準差。分析結果顯示因TEM影像解析度不足或是影像分析演算法參數不同所造成的量測誤差,可藉由平均後之應力應變曲線加上一正負標準差的範圍來定義誤差區間,此誤差區間可有效預測鋁合金拉伸試驗之加工硬化趨勢。 Here we present a novel computational framework to model the strengthening mechanism of Al-Mg-Si alloys caused by precipitation of Mg-Si compounds. Lightweight materials are crucial to develop the next generation of electronic cars in the automotive industry. Hence, aluminum alloy has been considered as a potential candidate. However, there was no comprehensive study to elucidate the strengthening mechanism from microscale. In this study, we developed a crystal plasticity model enhanced by geometrically necessary dislocations to incorporate the strengthening mechanism. The strengthening mechanism in Al-Mg-Si alloys is usually caused by the interaction between dislocations and Mg-Si based precipitates. Therefore, we implemented a dislocation-based crystal plasticity finite element method (CPFEM) which linked microscale dislocation density to mechanical properties to study the strengthening mechanism of Al-Mg-Si alloys due to precipitation. We obtained microscale information by incorporating TEM images as the input parameters directly without further curve fitting to predict the mechanical properties of the various artificial aging conditions. The simulation results showed a good agreement with yielding strength and ultimate tensile strength prediction of Al-Mg-Si alloys to different thermal processes. This study also provided a method to describe the uncertain parameters measured from TEM images, by averaging stress-strain curves from multiple samples and calculating the standard deviation. The results showed that the uncertainty caused by the resolution of TEM images or the image processing algorithm could be bounded by the average stress-strain curve plus and minus one standard deviation, and also agreed well with the work hardening prediction. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/68916 |
DOI: | 10.6342/NTU202003658 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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