Grain Structure and Microhardness Development of Twin-Roll Cast Aluminum Strips after Constrained Groove Pressing

Abstract

Twin-roll cast aluminum strips based on EN AW 3003 alloy with a small addition of Zr and Cr further processed by constrained groove pressing (CGP) were studied in this work. Vickers microhardness measurements were used to investigate an inhomogeneous distribution of microhardness as a result of an inhomogeneous strain distribution imposed by CGP. Results are consistent with the finite element method simulations of the total equivalent plastic strain which predicts higher accumulated strain in areas close to the edges of CGP dies. Microhardness saturates after two CGP cycles due to a dynamic recovery. Electron backscatter diffraction, light optical microscopy and transmission electron microscopy were used to study grain and dislocation structure and to compare domains with higher and lower microhardness. The sample after 3 CGP cycles exhibits an unusual mechanical behavior. Domains with higher microhardness exhibit a higher degree of recovery with a lower dislocation density than domains with lower microhardness.