Microstructure evolution, texture and strengthening mechanism of Al–Mg alloy with a square pyramid part during hot gas bulging with clustering balls

In the present work, the method of hot gas bulging with clustering balls (HGBB) was used to investigate the microstructure evolution, texture, and strengthening mechanism of Al–Mg alloys. After an alloy sheet was heated to 450 °C for 15 min, the square-pyramid shaped part was bulged by air at a pressure of 2 MPa. The ultimate tensile strength and hardness of the formed parts increased with the deformation, and the improvements in the most deformed area were by 30% and 40%, respectively, compared with the undeformed area. Microstructural and textural characteristics revealed that dynamic recovery occurred when the effective strain was 0.36, and new grains were created through dynamic recrystallization after the strain was further increased. The grains in the Cube {100} and Brass {110} orientations gradually increased with the deformation. Fine-grain strengthening, second-phase strengthening, and geometrically necessary dislocation density strengthening were the main strengthening mechanisms in the deformed area, which could be enhanced by the deformation during HGBB. A high dislocation density and low-angle grain boundaries were generated, accelerating and enhancing the precipitation and formation of fine recrystallized grains. The HGBB process yielded improved formability and mechanical properties of the formed parts. •A process of hot gas bulging with clustering balls (HGBB) is proposed to produce parts with complex shapes.•Enhanced mechanical properties during HGBB is achieved, and strengthening mechanisms is analyzed.•The microstructure evolution and texture in the forming process is discussed.