Analysis of micro void formation at grain boundary triple points in monotonically strained AA6022-T43 sheet metal

This study reports on the micro voids formed in a 1 mm thick sheet of rolled aluminum alloy AA6022 subjected to monotonic tensile loading. In this research micro voids were found to occur at certain grain boundary triple point (GBTP) junctions. The orientations of the grains at various GBTP junctions were determined using an electron backscatter diffraction detector mounted in a field-emission scanning electron microscope. Because damage evolution and eventual final failure are driven by local tensile hydrostatic stresses arising from microhetereogenities, the hydrostatic stress state surrounding the GBTP junction was evaluated using a crystal plasticity material model implemented in a finite element analysis code. Grain orientations that result in a local hydrostatic state of tension surrounding the GBTP junction were found to have a tendency to form micro voids.