Al-7Si-Mg鋁合金拉伸過程應變硬化行為及力學性能模擬研究

Al-7Si-Mg鋁合金拉伸過程應變硬化行為及力學性能模擬研究Modeling of the Strain Hardening Behavior and Mechanical Properties of Al-7Si-Mg Cast Aluminum Alloys during Tensile Process

建立了時效析出動力學模型、強化模型以及應變硬化模型，針對Al-7Si-Mg合金開展拉伸力學性能模擬研究。時效析出動力學模型可以模擬析出相密度、尺寸、分布、體積分數、基體中元素含量等微觀組織參數，并結合強化模型可以獲得合金的屈服強度。應變硬化模型可以模擬合金在拉伸過程的應力-應變曲線，并結合關系式(?UTS-?Y)=m??Y+n+f(Tss)可以獲得合金的抗拉強度和延伸率。首先模擬了Al-7Si-0.4Mg合金的析出相特征參數及屈服強度并進行實驗驗證，分析了模擬結果與實驗結果之間偏差產生的可能原因。采用應變硬化模型模擬了Al-7Si-0.36Mg合金在拉伸過程的應力-應變曲線，分析時效處理和鑄態組織細化程度對位錯存儲速率和動態回復速率以及合金的應力-應變曲線的影響規律。采用本模型預測了Al-7Si-0.4Mg合金在不同時效溫度下的抗拉強度和延伸率并與實驗結果進行對比，同時分析了二次枝晶臂間距對拉伸力學性能的影響。最后，對模型存在的局限性及影響拉伸力學性能預測精度的因素進行了分析。

Castings in Al-7Si-Mg alloys have an extensive applications in automotive industries, and the tensile properties including yield strength, ultimate tensile strength and elongation are commonly used to judge their mechanical properties. In this work, the precipitation kinetics model, yield strength model and strain hardening model have been used to predict the tensile properties in Al-7Si-Mg alloys. The precipitation kinetics model can be used to predict the precipitate microstructure parameters including the precipitate density, size, size distribution, volume fraction, and composition and so on, and through combining with the strength model, the yield strength can be obtained. The strain hardening model can be used to simulate the stress-strain curves during tensile process, and through combining with the experimental data fitted expression (?UTS-?Y)=m??Y+n+f(Tss), the ultimate tensile strength and elongation can be obtained. First, the evolution of precipitate microstructure parameters and yield strength as a function of aging time was simulated and a comparison with the experimental results was made. The possible reasons resulting in the deviation between simulated and experimental yield strength were analyzed. The stress-strain curves during tensile process of Al-7Si-0.36Mg alloy were simulated using strain hardening model, and the influence of aging treatment and as-cast microstructure refining scale on the parameters of dislocation storage rate and dynamic recovery rate as well as the stress-strain curves was analyzed. Then, the ultimate tensile strength and elongation of Al-7Si-0.4Mg alloy aged at different temperatures were predicted and compared well with the experimental results, and the influence of secondary dendrite arm spacing on tensile properties was analyzed. Finally, the limitation of present model and the factors influencing the prediction precision of tensile properties were outlined.

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