Effect of heating rate during solution treatment on the bendability of Al–Mg–Si alloys

Abstract

The bendability of Al–Mg–Si alloy sheets is a key parameter for their application as skins of automotive body panels. In the present study, the influence of heating rate on the bendability of Al-0.6Mg-1.0Si (in wt%) alloy was investigated using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The bendability of Al–Mg–Si alloy was found to be significantly dependent on the heating rate of solution treatment. After bending, the rapidly heated specimen exhibited only slight surface undulation, while the slowly heated specimen showed severe surface necking and even micro-cracks. The severe surface necking was caused by intensive shear bands formed during bending, and the micro-cracks were the results of the interaction between the intensive shear bands and coarse second phase particles. Elongated coarse grains were more likely to produce intensive shear bands, and cube-oriented grains impeded the formation of shear bands. The schematics of recrystallization and bending processes for Al-0.6 Mg-1.0 Si alloy considering two different heating rates are proposed.