Microstructures evolution and mechanical properties of 5052 aluminium alloy processed by constrained groove pressing

Abstract

Commercial 5052 aluminium alloy sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP) at room temperature. The impact of repeated CGP, upon the microstructure refinement was investigated by polarised optical microscope as well as transmission electron microscope. Changes in mechanical properties, measured by tensile test and hardness test, were related to the evolution of microstructures. Moreover, the microhardness, measured on the polished cross-section of each as-pressed sheet, was plotted to provide a pictorial depiction of the homogeneity. The results show that the mechanical fragmentation dominates at grain refinement and a submicron grain size of about 300 nm was achieved in 5052 aluminium alloy sheets by imposing severe plastic strains of 4.64 utilising the CGP technique. The average microhardness increase dramatically after one pass and then slightly increases with increasing passes, but the homogeneous distribution of microhardness decreases after one pass and then recovers in subsequent passes result in the corresponding uniform distribution of microstructure. In addition, the ultimate tensile strength clearly increases with increasing passes and the elongation decreases after one pass and then remains reasonably constant with further passes.