物理概念的本構(gòu)關(guān)系
(西北工業(yè)大學(xué) 航空學(xué)院，西安 710072)
摘 要: 利用準(zhǔn)靜態(tài)試驗(yàn)機(jī)以及Hopkinson壓桿裝置對(duì)AZ31鑄造鎂合金在不同應(yīng)變速率和不同溫度下的塑性流動(dòng)性能進(jìn)行研究，結(jié)合金相顯微技術(shù)對(duì)試驗(yàn)后的試樣進(jìn)行微觀分析。結(jié)果表明：在低應(yīng)變速率下，隨著溫度的升高，AZ31鎂合金發(fā)生明顯的由脆性到韌性的轉(zhuǎn)化，其轉(zhuǎn)化溫度為473 K左右；當(dāng)應(yīng)變速率增加到1.2×104 s−1時(shí)，會(huì)發(fā)生脆化現(xiàn)象，塑性變形能力變差。基于微觀分析，低應(yīng)變速率下晶體中孿晶的存在是促進(jìn)材料塑性變形增加的主要因素。而在高應(yīng)變速率下，動(dòng)態(tài)再結(jié)晶和第二相粒子沉淀硬化顯著地影響金屬的塑性變形。結(jié)合系統(tǒng)的試驗(yàn)結(jié)果，基于熱激活位錯(cuò)機(jī)制，建立一種物理概念的塑性流動(dòng)本構(gòu)模型，對(duì)較高應(yīng)變速率和不同溫度下的流動(dòng)應(yīng)力進(jìn)行模型預(yù)測(cè)。通過(guò)對(duì)比，模型預(yù)測(cè)結(jié)果與試驗(yàn)數(shù)據(jù)吻合較好。
關(guān)鍵字: AZ31鎂合金；塑性流動(dòng)；應(yīng)變速率；微觀機(jī)理；本構(gòu)關(guān)系
constitutive relation for AZ31 cast magnesium alloy
（School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The plastic flow properties of cast magnesium alloy AZ31 were studied at different strain rates and temperatures by using quasi-static testing machine and Hopkinson pressure bar equipment. The microstructure analysis of deformed specimen was carried out by means of the metallography microscope technique. The results show that, at lower strain rates, the transformation of AZ31 alloy from brittleness to toughness occurs with increasing temperature, and the transformation temperature is about 473 K. The brittleness phenomenon happens with increasing strain rate to 1.2×104 s−1, and the plastic deformation capability becomes weak. Based on the microstructure analysis, the key factor of the plastic deformation enhancement at low strain rates is due to the existence of twinning in the crystal. At higher stain rates, however, the dynamic recrystallization and second phase particle precipitation hardness strongly affect the metal plasticity. Based on the thermal activation dislocation mechanism, paralleled with the system testing results, a plastic flow constitutive model with the physical conception was established. The model was used to predict the plastic flow stress at different temperatures and higher strain rates. According to comparing results, good agreement between the model predictions and experimental results is obtained.
Key words: AZ31 magnesium alloy; plastic flow; strain rate; microstructure mechanism; constitutive relation
