Al-Mg-Si合金針棒狀析出相時效析出動力學及強化模擬研究

Al-Mg-Si合金中針棒狀析出相時效析出動力學及強化模擬研究MODELLING INVESTIGATION OF PRECIPITATION KINETICS AND STRENGTHENING FOR NEEDLE/ROD-SHAPED PRECIPITATES IN Al-Mg-Si ALLOYS

通過與計算相圖數(shù)據(jù)庫相耦合, 建立了 Al-Mg-Si 三元合金體系中針棒狀析出相時效析出動力學和時效強化模型, 考慮了析出相形貌對形核、生長、粗化以及強化效果的影響. 通過該模型可以獲得不同時效工藝下析出相微觀組織特征參數(shù)的變化及對應的屈服強度變化. 利用該模型模擬了 Al-Mg-Si 合金在不同時效工藝條件下的時效析出過程和屈服強度變化, 并與實驗結(jié)果及 Lifshitz-Slyozov-Wanger 粗化模型計算結(jié)果進行了對比. 基于模型研究并分析了析出相長徑比、界面能、合金元素含量以及析出相成分對 Al-Mg-Si 合金時效析出動力和強化效果的影響. 結(jié)果表明: 不同的界面能和長徑比會影響形核密度和析出相尺寸, 進而影響合金屈服強度. 增加基體中 Mg 含量可以促進時效析出, 提高合金屈服強度, 而基體中 Si 含量的增加對合金屈服強度并不產(chǎn)生明顯影響.

The aging hardening is the main strengthening mechanism of Al-Mg-Si alloys, and the hardening effect is determined by the microstructural features of precipitates including the morphology, composition, volume faction, nucleation density as well as the size distribution. In present work, an integrated mathematical model coupling with the CALPHAD software is developed to simulate the precipitation kinetics and strengthening effects of needle/rod-shaped precipitates in ternary Al-Mg-Si aluminum alloys. This model takes into account the effects of morphology on the nucleation, growth and coarsening of precipitates and on the strengthening effects. The yield stress model accounts for the whole precipitate size distribution, shape of precipitates and their specific spatial distribution based on the consideration of the competing shearing and bypassing strengthening mechanisms. Application of the model to various aging treatments of Al-Mg-Si alloys is conducted and the predictions both for microstructural features and yield stress are validated with experimental results and the predictions by LSW model. Using this model, the effects of aspect ratio, interfacial energy, alloy composition and Mg/Si atom ratio in precipitates on precipitation kinetics and yield stress are investigated and analyzed. The results reveal that the different interfacial energy and aspect ratio will affect the predicted density and size of precipitate, and further has an influence on the prediction precision of yield stress. An increase of Mg content in the matrix of Al-Mg-Si alloy will accelerate the precipitation and improve the yield stress, while increasing the Si content in the matrix will produce little influence on the yield stress.

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