Al-7Si-Mg鋁合金拉伸過程應(yīng)變硬化行為及力學(xué)性能模擬研究

Al-7Si-Mg鋁合金拉伸過程應(yīng)變硬化行為及力學(xué)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(shí)效析出動(dòng)力學(xué)模型、強(qiáng)化模型以及應(yīng)變硬化模型，針對(duì)Al-7Si-Mg合金開展拉伸力學(xué)性能模擬研究。時(shí)效析出動(dòng)力學(xué)模型可以模擬析出相密度、尺寸、分布、體積分?jǐn)?shù)、基體中元素含量等微觀組織參數(shù)，并結(jié)合強(qiáng)化模型可以獲得合金的屈服強(qiáng)度。應(yīng)變硬化模型可以模擬合金在拉伸過程的應(yīng)力-應(yīng)變曲線，并結(jié)合關(guān)系式(?UTS-?Y)=m??Y+n+f(Tss)可以獲得合金的抗拉強(qiáng)度和延伸率。首先模擬了Al-7Si-0.4Mg合金的析出相特征參數(shù)及屈服強(qiáng)度并進(jìn)行實(shí)驗(yàn)驗(yàn)證，分析了模擬結(jié)果與實(shí)驗(yàn)結(jié)果之間偏差產(chǎn)生的可能原因。采用應(yīng)變硬化模型模擬了Al-7Si-0.36Mg合金在拉伸過程的應(yīng)力-應(yīng)變曲線，分析時(shí)效處理和鑄態(tài)組織細(xì)化程度對(duì)位錯(cuò)存儲(chǔ)速率和動(dòng)態(tài)回復(fù)速率以及合金的應(yīng)力-應(yīng)變曲線的影響規(guī)律。采用本模型預(yù)測(cè)了Al-7Si-0.4Mg合金在不同時(shí)效溫度下的抗拉強(qiáng)度和延伸率并與實(shí)驗(yàn)結(jié)果進(jìn)行對(duì)比，同時(shí)分析了二次枝晶臂間距對(duì)拉伸力學(xué)性能的影響。最后，對(duì)模型存在的局限性及影響拉伸力學(xué)性能預(yù)測(cè)精度的因素進(jìn)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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