Pressure infiltrated syntactic foams—Process development and mechanical properties

The pressure infiltration process for the production of aluminium syntactic foams incorporating 45 and 270 μm ceramic microspheres in nominally 1350, 5083 and 6061 aluminium alloy matrices was studied. Minimisation of vacuum level, heating rate and infiltration temperature was found to allow the production of foams with very low levels of unintended porosity. Infiltration temperatures at or below the liquidus were shown to minimise the amount of dissolution of spheres in the matrix, giving increased certainty over matrix composition and in the case of the 1350, 270 μm diameter, high compressive strength and strain energy. The foams remained intact at strains up to 50% despite significant fracturing, resulting in high and repeatable strain energies that make these materials suitable for many energy absorbing applications. Further, different alloy–sphere-temperature combinations displayed a range of compressive stress–strain characteristics that give potential for tailoring these materials to different applications. Tensile and bend tests confirmed that failure in tension is brittle with maximum tensile strengths of 94 MPa.