Processing, Properties and Coating of Micro‐Porous Syntactic Foams

There exists a wide range of techniques for the production of porous metal structures. [1,2] Several methods are based on the infiltration of a pattern with metal melts leading as well to open porous as to close cell structures. For open porous structures the pattern has to be removed after infiltration e.g. by leaching or pyrolysis. [2,3] If the infiltrated pattern consists of hollow spheres which remain in the metal matrix after infiltration the resulting closed-cell structure is referred to as “syntactic” foam. Investigations for metal syntactic foams are known e.g. for aluminium, titanium or magnesium alloys. [4–6] Different techniques were used, mostly gas-pressure-assisted but also spontaneous infiltration. [6–8] In the majority of the investigations macroscopic hollow spheres with diameters ranging from 0.5 mm to 5 mm were used. Balch et al. infiltrated loose packings of microscopic scale ceramic micro-spheres with commercial-purity aluminium and 7075 aluminium alloy. [4] They could produce specimen with relatively high densities of about 1.40 g/cm 3 and 1.66 g/cm 3 which had peak compression strengths of over 100 MPa and excellent energy absorbing capability. The technological approach presented in this work is close to the investigations of Balch et al.