中文摘要：

为了探索应变速率对超细晶材料高温变形特点的影响,通过压缩实验以及显微观察,系统研究在不同温度和应变速率下等通道转角挤压Al的变形和损伤特点以及显微微组织。结果表明:应变速率的提高消除了等通道转角挤压Al在变形温度T≤473 K时表现出的应变软化现象,并且大大提高了变形温度在473573 K范围的屈服强度和流变应力。等通道转角挤压Al的塑性变形主要由剪切变形控制。当应变速率为1×10-3s-1时,变形温度T≥473 K时可观察到沿剪切带形成了大量裂纹,并且二次剪切带基本消失。而当应变速率为1×10-2s-1时,只有在变形温度低于473 K时才能观察到沿剪切带形成的裂纹,并且当压缩温度T≥473 K时,二次剪切带变得更加清晰。等通道转角挤压Al的显微组织主要由亚晶组成,应变速率的提高抑制了亚晶的长大,从而导致高温屈服强度和流变应力的提高。

英文摘要：

To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain ratesε were systematically studied through compression tests and microscopic observations. The increase in ε eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473?573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10?3 s?1; however, at 1×10?2 s?1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ε inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.