Stabilization and Deformation Behaviour of In Situ Al3Zr/AA6061 Composite Aluminium Foams

Aluminium foam offers an exceptional strength-to-weight ratio and energy absorption capacity, but variations in the cell structure hinder its performance and limit industrial applications. The addition (ex situ) or formation (in situ) of specific particles during the processing of metal foams stabilizes the foam by restricting the cell coalescence and liquid drainage during foaming. In this study, we investigated the potential of in situ formed Al3Zr particles to enhance the stability and properties of AA6061 closed-cell foams. The microstructure analysis revealed the presence of Al3Zr particle clusters along the plateau borders, inhibiting cell coalescence and wall thinning. Consequently, the composite foams exhibited a 37 pct increase in plateau stress and a 56 pct increase in energy absorption capacity, with a 78.5 pct mean energy absorption efficiency compared with base AA6061 foams. The coefficient of thermal expansion mismatch of particles with the matrix is the primary strengthening mechanism, leading to a 12.9 pct improvement in the yield strength of the composite. The mesoscale ex situ compression test showed a brittle failure mode with premature cell fracture due to the formation of microcells and secondary phases within the cell edge region. The fractography revealed a mixed mode of ductile and brittle failure with debonding of the secondary phase network and fracture of in situ Al3Zr particles.