Strain path effects on microstructural evolution and mechanical behaviour of constrained groove pressed aluminium sheets

Abstract

Change in strain path during severe plastic deformation (SPD) of metallic materials has shown significant influence on the microstructural evolution, grain boundary characteristics and mechanical behaviour. In the present work high purity aluminium sheets are severe plastically deformed at room temperature by conventional constrained groove pressing (CGP) technique and cross-CGP technique up to 2,4, and 6 passes thereby imparting total effective plastic strain of 2.32, 4.64 and 6.96 respectively. Change in strain path is imposed during cross-CGP by rotating the sheets by ±90° along thickness axis between each pass. Microstructural evolution of processed sheets studied by electron back scattered diffraction (EBSD) analysis revealed ultra-fine grains (~1μm) irrespective of change in strain path. Analysis of grain boundary characteristics showed significant influence of strain path change on the evolution of relative fraction of low angle and high angle boundaries. The grain refinement mechanism during deformation processing in both conventional CGP and cross-CGP is corroborated to the evolution of misorientation distribution. Though considerable improvement in room temperature tensile characteristics is observed in both cases, cross-CGP processed Al sheets exhibited superior tensile properties.