Dynamic Characterization and Modeling of Ductile Failure of Sintered Aluminum Alloy through Shear-compression Tests

This work presents an experimental method using shear-compression tests allowing the study of the temperature and strain rate sensitivities of the failure mechanisms of sintered metallic materials presenting low intergranular cohesion. Indeed, the classical approach using tensile tests cannot be used for such materials because only the intergranular resistance of the grains powder is therefore measured. The shear-compression tests allow the deformation of the grains powder and prevent the failure by decohesion. In this study, the failure behaviors of a sintered 7020 and laminated AA7020-T651 aluminum alloys are thoroughly investigated by means of shear-compression tests (several geometries) and specific expressions leading to modeling are provided and discussed. The modeling of the temperature sensitivity of the strain at initiation of failure is performed with a specific physical expression which takes into account the change of microstructure and present a temperature-strain rate coupling. Furthermore, it is linked to the thermal evolution of the stress and uses the same set of parameters determined for the stress modeling. Finally, a method using this expression is suggested in order to uncouple the phenomena responsible of the increase of the strain at initiation of the failure: the effect of the strain rate alone and the softening due to the adiabatic heating.