超细晶纯铝微塑性变形本构关系的建立

Constitutive relationship of micro-deformation in an ultrafine-grained pure aluminum

为了研究超细晶纯铝热变形行为,利用等通道挤压工艺制备了超细晶纯铝,并采用INSTRON 5965材料电子万能试验机对超细晶纯铝进行了高温微压缩实验,分析了超细晶纯铝在150~250℃、应变速率3.3×10^-4-1×10^-1s^-1条件下流动应力的变化规律.研究表明,流动应力随试样尺寸的减小呈下降趋势,且变形温度和应变速率对流动应力有显著影响,流动应力随变形温度的升高和应变速率的降低而降低.基于双曲正弦形式修正的Arrhenius关系的本构模型,建立了超细晶纯铝高温微压缩变形本构关系.实验验证表明,所建立的本构关系能够较好地反映超细晶纯铝高温微塑性变形行为特征.

In order to study the high-temperature flow stress of ultrafine-grained pure aluminum,ultrafinegrained pure aluminum was prepared by equal-channel angular pressing（ ECAP）. Micro-compression tests of ultrafine-grained pure aluminum at high temperature were performed on INSTRON 5965 at the deformation temperatures varying from 150 to 250 ℃ and strain rates ranging from 3.3×10^-4-1×10^-1s^-1. The flow stresses in different deformation conditions were investigated. The results show that the flow stress trends to decrease with the decreasing of sample sizes. The flow stresses are also significantly affected by both deformation temperature and strain rate. The flow stress decreases with the deformation temperature increasing and strain rate decreasing. Using the modified Arrhenius equation,the hot micro-deformation constitutive relationship is established in consideration of strain. The predicted flow stress curves using the proposed constitutive equations well agree with the experimental results of the flow stress of micro-compression at high temperature for ultrafine-grained pure aluminum.