Recyclabilité des alliages d'aluminium de fonderie : Influence des éléments résiduels sur la microstructure et le comportement mécanique

Cast aluminium alloys make popular candidates for automotive applications and in particular on the fabrication of cylinder head and engine block materials. For the development of a new cylinder head and in order to lower the costs of provision at the refiner, we have chosen to increase the iron, manganese, and zinc contents used in AS7U3G alloys. The effect of residual element on the microstructure and mechanicals properties of two cast aluminium alloys, the reference AS7U3G and the AS9U3G with a high content in residuals elements, in T5 state, has been studied. Fatigue, tensile, and microhardness tests were performed and the test data were analyzed in relation with the evolution of microstructure. The results of tensile and low cycle fatigue tests showed that stresses levels in the two alloys were identical, but some differences appear at the level of precipitation evolution; And the fatigue life defers considerably because of the significant number of intermetallics compounds and volume fraction of pores in the AS9U3G alloy which are fatigue cracks initiation sites.