Characterisation of hybrid metal matrix syntactic foams

High quality aluminium matrix syntactic foams (AMSFs) were produced by pressure infiltration. This method can ensure the maximal volume fraction of the reinforcing hollow spheres and very low amount of unwanted or matrix porosities. By this method hybrid MMSFs with mixed metal and ceramic hollow spheres were also produced. The matrix material was AlSi12 alloy and two different types – produced by Hollomet GmbH in Germany – of hollow spheres were used: Globomet (GM) and Globocer (GC). The geometrical properties of the hollow spheres were similar (average outer diameter), but their base material was pure iron and Al2O3+SiO2 in the case of GM and GC hollow spheres respectively. The volume fraction of the reinforcing hollow spheres were maintained at ~65 vol%, but the ratio of them was altered in 20% steps (100% GM + 0% GC, 80% GM + 20% GC…). The results of the compression tests showed, that the compressive strength, yield strength, plateau strength, structural stiffness and the absorbed mechanical energy values increased with higher ceramic hollow sphere reinforcement ratio. The fracture strains of the investigated MMSFs decreased with the higher GC ratio. Generally the strength values also increased with higher diameter to height (H/D) ratio from H/D=1 to H/D=1.5 and 2