Strain rate-dependent high temperature compressive deformation characteristics of ultrafine-grained pure aluminum produced by ECAP

To explore the effect of strain rate 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 rates were systematically studied through compression tests and microscopic observations. The increase in 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 inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.