鋁合金7075-T651動態(tài)流變應力特征及本構模型Dynamic flow stress characteristics and constitutive model of aluminum 7075-T651

為了研究鋁合金7075-T651的流變應力變化特征，在高溫分離式霍普金森壓桿裝置上對圓柱試樣進行了溫度范圍25~400 ℃及應變率范圍600~12 000 s^-1的動態(tài)壓縮試驗。結果表明：鋁合金7075-T651的流變應力對應變率不敏感，對溫度有較強的敏感性?？傮w上，流變應力隨溫度的升高而減小，但在350~400 ℃時流變應力差別很小。在高應變速率時，當應變超過一定水平時，應力出現(xiàn)急劇減小，材料發(fā)生失效。通過變形后試樣的微觀組織觀察可以發(fā)現(xiàn)，應變速率較高時出現(xiàn)絕熱剪切帶是材料流變應力急劇減小的主要原因。在實驗數(shù)據(jù)基礎上，建立了一個基于物理概念的鋁合金7075-T651本構模型預測其流變應力，與實驗對比表明，所建立的本構模型在較寬的溫度和應變速率范圍內能夠很好地預測鋁合金7075-T651的流變應力。

To understand the flow stress characteristics of aluminum 7075-T651, dynamic compression tests during the temperature range of 25-400 ℃ and strain rate range of 600-12 000 s^-1?were performed on cylindrical samples using SHPB technique. The results show that the flow stress of aluminum 7075-T651 is strongly sensitive to temperature compared with strain rate, the flow stress reduces with the increase of temperature. There is a temperature range between 350-400 ℃ where the flow stress doesn’t depend on temperature, showing little difference. At high strain rate when the strain exceeds one certain level, the flow stress decreases sharply and the sample fails. Through the observation of cross-section microstructure of deformed sample, the shear band is responsible for the rapid reduction of flow stress. Finally based on experimental data, a physically based constitutive model is given to depict the flow stress of the aluminum. The model predictions are compared with the results of experiments. Good agreement between the theoretical predictions and experimental results is obtained. The given constitutive model can predict the flow stress of aluminum 7075-T651 in a wide range of temperatures and strain rates.

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