Synthesis of syntactic steel foam using mechanical pressure infiltration

Steel foam offers potential advantages over aluminum foams and other metallic foams. The inherent strength of steel combined with the reduced density of foam presents an attractive material with greater strength and modulus than light alloy foams, greatly reduced density relative to solid steel, and efficient energy absorption. However, thus far there have been few reports describing efforts to produce steel foam, and these have relied on powder metallurgical approaches as opposed to molten state processing. This study demonstrates a feasible synthesis method to consistently produce lab-scale foam samples with uniform distributions of microspheres and negligible unintended porosity using a simple liquid state method of infiltration. To accomplish this, the effects of process parameters were investigated. The preheatment temperature of the microspheres must be close to the melting temperature of steel and a minimum pressure must be exerted to produce the steel infiltration into the microspheres. Syntactic foams with relative density of 0.54 were achieved. The resultant syntactic foams were characterized by chemical analysis, microstructural analysis and hardness measurement. The basic mechanical properties of two different steel compositions were studied under compression loading, Please cite this article as Castro and S. Nutt , " Synthesis of syntactic steel foam using mechanical pressure infiltration " Mater Sci & Engrg A 535 (2012) 274-one with a ferrite microstructure and the other with a pearlite microstructure. The pearlite foam has greater compression strength and energy absorption capacity than the ferrite foam. The properties of the steel syntactic foams were compared to those of steel foams reported elsewhere. Prospects and challenges for achieving higher energy absorption capacity are discussed.