Constrained groove pressing (CGP): Die design, material processing and mechanical characterization

Abstract

Constrained groove pressing (CGP) is a severe plastic deformation (SPD) technique used as a strengthening method for sheet metal. In the current work, an optimal/cost-saving design for CGP dies was attained using the stress analysis tool in SolidWorks Simulation Xpress wizard. This study examined low-cost and widely industrially applied aluminium materials, i.e., pure 1050 Al and 5052 Al alloy. Each material was subjected to three passes of the CGP process using a 150 tons capacity press. For both materials, inter-pass annealing treatment was undertaken before the third pass. The effect of the number of CGP passes on the microstructure and tensile properties was studied after each pass. For CGPed pure 1050 Al with respect to the as-received material, the ultimate tensile strength (UTS), yield strength (YS) and YS/UTS ratio increased with an increasing number of CGP passes until the second pass, while elongation decreased with the number of passes. For CGPed 5052 Al alloy, the UTS and YS increased after the first pass and then decreased after the second pass. Variations in the elongation and YS/UTS ratio of 5052 Al alloy after the CGP process were insignificant. After inter-pass annealing and applying the third CGP pass, the strength of pure 1050 Al decreased, and that of 5052 Al alloy increased, which was attributed to the influence of composition on their structures. The strength-ductility balance decreased with an increasing number of CGP passes in both materials.