The effect of Mg and Si content on the microstructure,texture and bendability of Al-Mg-Si alloys

摘要

In this paper, four model Al-Mg-Si automotive sheet alloys with different Mg and Si contents were prepared and heated treated to the same T4P temper (solution treated and pre-aged for 8 h at 75 °C and aged for 1 week at room temperature). The influence of the Mg and Si content on microstructure, crystallographic texture, tensile behavior and bendability was investigated. The evolution of microstructure and texture during thermo-mechanical processing was characterized. It was found that the bendability of sheets in the T4P temper decreases with raising Mg and Si content. The deterioration of bendability can be related to the decreased true fracture strain measured in tension. The fracture mode in the bend tests was found to be predominately transgranular. Crack initiation was observed at α-Al(FeMn)Si constituent particles and the propagation of cracks proceeded by a combination of shear bands and void growth/coalescence. Finally, the strength of the recrystallization texture increases was observed to increase with increasing Mg and Si contents and it was found that the relationship between crystallographic texture and the plastic anisotropy, e.g. r-value, could be predicted using the visco-plastic self-consistent (VPSC) polycrystal plasticity model.