The impact of thermo-mechanical processing routes on product quality in integrated aluminium tube bending process

Abstract

In response to the increased demand for high dimensional accuracy and mechanical properties of formed metal products, this research aims to provide new insights into the impact of thermo-mechanical processing routes on quality in integrated bending process for heat-treatable aluminium tubes. Based on carefully controlled experiments with four representative processing routes, including R1: solution-heat-treatment (SHT) → bending → artificial aging (AA), R2: SHT → bending → natural aging (NA), R3: SHT → NA → bending → AA, and R4: SHT → NA → bending, the impact of these routes on final geometrical dimensions and mechanical properties of bent parts is thoroughly evaluated. As compared with R2 and R4 routes employing naturally-aged tubes in the bending operation, R1 and R3 routes with bending of SHT tubes significantly reduce both springback by 50 % and wall-thinning by 26 %. Considering product strength, however, for the routes with AA, R3 can achieve 16 % improvement of the hardness as compared to R1; for the routes without AA resulting in products in T4-temper, R4 can make the average hardness 20 % higher than R2. Moreover, R1 and R3 routes can make a more uniform hardness distribution in the cross-section of bent tubes than the two others, meaning that AA reduces the hardening effect of pre-deformation. All these findings provide a knowledge basis for the selection of suitable processing routes as well as the design of new, customized processing routes for the efficient manufacture of value-added aluminium tubular products.