Effects of constituent particle content on ductile fracture in isotropic and anisotropic 6000-series aluminium alloys

Tension tests on smooth and notched specimens were conducted for four 6000-series aluminium alloys to assess the effects of constituent particles on ductile fracture at different stress states. Two of the alloys are engineering materials, while the remaining two were tailor-made to be similar to the engineering materials but with more than three times the amount of constituent particles. The microstructure of both isotropic (cast and homogenised) and anisotropic (extruded) materials was characterised using scanning electron microscopy (SEM), optical microscopy and X-ray diffraction. Axisymmetric smooth and notched specimens were machined from cast and homogenised billets and extruded profiles. All specimens were tested in the artificially aged T6 temper. The specimens were strained in tension until fracture, and the fracture surface of the specimens was later investigated based on SEM images. The experiments show that the ductility is significantly improved by extrusion, while a high stress triaxiality and a high volume fraction of large-sized constituent particles have a detrimental effect on the ductility. However, the negative effect of the increased particle volume fraction on ductility was markedly reduced after extrusion. The experiments also indicated that a larger amount of constituent particles may improve the ductility under certain conditions