Effect of the Porous Skeletal Iron Structure on the Infiltration of Aluminum Melts

The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was studied. The densification of compacts made of iron powder with various blowing additions was examined. The minimum pressures at which 35–40% porosity was reached were found to be 150–200 MPa. The use of metal iron shavings allowed a porous skeleton to be formed at a lower pressure (100 MPa). The minimum pore size (400 μm) ensuring complete filling of the porous skeleton with an aluminum melt heated to 760–780°C under a pressure gradient was established. The potential production of iron–aluminum composites without the formation of chemical compounds was shown. A thin discrete layer 5–10 μm thick was observed at the interface between iron and aluminum, where the iron skeleton became saturated with aluminum. This layer provides better adhesion between the iron skeleton and the aluminum melt. The absence of chemical compounds in the Fe–Al system in impregnation conditions is explained by the process kinetics: the components cannot react with each other within several seconds. The effect exerted by the type of porous skeletal structure on the compressive strain of the iron–aluminum composites was established. The greatest compression strength (~400 MPa) was shown by the samples produced from 3D skeletons. The stress–strain curves for the samples with 3D skeletons show two bends: one is in the range 60–70 MPa (beginning of plastic deformation) where strain hardening occurs and strain increases to 20–22% and the other begins at 230–240 MPa and determines the bulk deformation of the samples. The highest yield stress was observed for the samples with shavings-based skeletons (115.2 MPa), which is associated with a high contact surface area of the shaving particles that are randomly intertwined. Accordingly, the lowest characteristics were shown by the samples with skeletons consisting of powder particles with the minimum contact area.