Porous graded FeAl intermetallic foams fabricated by sintering process using NaCl space holders

A fabrication method for the FeAl intermetallic based porous graded materials (PGMs) is described and discussed in detail in the present paper. A multi-step manufacturing process for the FeAl PGMs is proposed. Open-cell FeAl PGMs with adjustable porosity and corresponding mechanical properties have been successfully prepared using the NaCl preforms via a sintering-dissolution process. The FeAl PGMs were obtained from the Fe and Al elemental powder mixtures and NaCl powder with a varying particle size. A quantitative metallographic evaluation of both chemical and phase composition shows that obtained PGMs are characterized by a homogeneous FeAl intermetallic matrix exhibiting a graded distribution of the pore size within the range 0.6–2 mm and porosity from 40% to 60%. Moreover, a proper preparation of the batch material allows obtaining a discrete or quasi-continuous porosity gradient. Mechanical properties of the fabricated FeAl PGMs were examined in static compression tests. It was observed that sample destruction started in the area of the smallest pores (weakest link) through a walls shearing and crushing mechanism. The quasi-continuous PGMs exhibit a nearly twice higher compressive strength than that for samples with the discrete gradient.