Numerical simulation and experimental study of laser bending of 7075 aluminum alloy thin sheets

Abstract Laser bending is a die-less process suitable for hard-to-form 7075 aluminum alloy sheets, but its multi-pass deformation behavior and associated property changes remain insufficiently quantified. This study combined a three-dimensional thermo-mechanically coupled finite element model with experiments on 3 mm-thick 7075-T6 sheets to determine the effects of laser power, scanning speed, spot diameter, and scanning passes on bending angle, microstructure, and hardness. After experimental validation, microstructural evolution and property changes in the bending zone were examined using optical microscopy, Vickers microhardness testing, and x-ray diffraction (XRD). Validation against measured bending angles and residual bending-height profiles yielded a mean bending-angle error of 5.64%, a mean relative profile difference of 7.78%, a root-mean-square error of 0.332 mm, and a coefficient of determination of 0.969 after six passes. The results indicated that the bending angle was governed by heat input and the through-thickness temperature gradient, with the latter playing the dominant role. The angle peaked at a line energy density of 26.00 J·mm −2 , and parameter influence was ranked as number of passes > spot diameter > laser power > scanning speed. The maximum angle of 7.649° occurred at 750 W, a 5 mm spot, twelve passes, and 5 mm s −1 . For practical processing, 650 W, 5 mm s −1 , a 5 mm spot, and six passes were preferred, producing 3.900° without surface ablation. XRD revealed no new phases but a reduced mean peak width, while elongated rolled grains transformed into fine equiaxed grains. The mean Vickers hardness decreased from approximately 165 HV to 128.62–139.36 HV because of precipitate dissolution and coarsening, although grain refinement and short-duration re-precipitation at 650 W partially mitigated the softening. This study provides guidance for precision laser forming of 7075 aluminum alloy sheets.