Curvature, microstructure, and mechanical property of an asymmetric aluminium profile produced by sideways extrusion with variable speed

Abstract

Sideways extrusion is an advanced technology for one-step production of curved profiles eliminating the need for subsequent bending processes. Its effectiveness in controlling the bending curvature of symmetric products has been well established in prior research. However, there is no report on the effect of asymmetric product shape on bending curvature and still lacking quantitative analysis of welding quality and microstructure of the extrudate for the sideways extrusion, limiting its application scope. In this study, an asymmetric Z-shape aluminium profile was manufactured using sideways extrusion at different speeds and the corresponding numerical simulation was conducted to analyse the extrudate shape, welding quality, microstructural and mechanical properties. The bending mechanism of extrudate, resulting from the non-uniform metal flow during extrusion, was identified. The curvature radius was found to depend on the average exit velocity and the velocity gradient along the transverse direction both of which increase with increasing extrusion speed. Improvements in welding quality and increased recrystallisation fraction during extrusion were quantitatively predicted using developed subroutines and these predications aligned well with the results from post-extrusion examination. In addition, tensile test results differed for profile sections extruded at different speeds, which were attributed to the combined effect of welding quality, work hardening, recovery and continuous dynamic recrystallisation.