Unraveling the formation mechanism of deformation bands in AA1100 alloy during plane forging and return-plane forging

•The formation mechanism of DBs observed in AA1100 after PF and R-PF during MADF was unraveled by microtexture analysis.•Calculation of the lattice rotation rate and the divg˙ was used to evaluate the kinematic stability of deformed grains under the R-PF.•The heterogeneity of the orientation stability was used to explain the development of the DBs in the R-PF specimen.•CPFEM successfully simulated the development of DBs within deformed grains during the R-PF.•The heterogeneity of orientation stability occurring within the blurry bands enhanced the formation of DBs in the deformed grains during the R-PF. In this study, the formation mechanism of deformation bands (DBs) observed in AA1100 after plane forging (PF) and return-plane forging (R-PF) during multi-axis diagonal forging (MADF) was unraveled via microtexture analysis using a rate-sensitive model and crystal plasticity finite element method (CPFEM). Blurry bands with an orientation relationship of mainly LAGBs were developed in the deformed grains in the PF specimen. The heterogeneity of the orientation stability (Q) that occurred within the blurry bands and their surrounding regions contributed to the development of the DBs in the deformed grains in the R-PF specimen. Microstructure-based CPFEM successfully simulated the development of DBs within deformed grains during R-PF. CPFEM revealed that heterogeneity of the crystallographic orientation that occurred within the blurry bands and their surrounding regions inside the PF specimen was the main cause of the formation of DBs in the deformed grains during R-PF. Graphical Abstract [Display omitted] .