Influence of heat treatments on the microstructure and mechanical behaviour of open cell AlSi7Mg0.3 foams on different lengthscales

Abstract This paper reports about the influence of different heat treatments such as solution annealing (W) and solution annealing plus ageing (T6, T7) on the microstructure of AlSi7Mg0.3 open cell foams and their effect on the mechanical properties. The mechanical properties and the local failure mechanisms of individual struts and foam specimens have been evaluated by micro-hardness measurements and micro-tensile testing of struts as well as in-situ compression tests on foam samples, combined with scanning and transmission electron microscopic evaluation of the microstructure. Contrary to published results for the bulk material, we only found a weak influence of the heat treatments on the struts' and foams' mechanical properties. We assume that this is mainly due to the inhomogeneous microstructure of the struts with coarse plate-shaped Si phases, leading to a subordinate effect of the precipitates formed during the heat treatments. The morphology of the coarse Si and intermetallic phases is only slightly influenced by the heat treatments, but profoundly determines the deformation, cracking and failure behaviour of the struts and thus of the entire foam.