EFFECT OF THE POROUS SKELETAL IRON STRUCTURE ON THE INFILTRATION WITH ALUMINUM MELT

Abstract

The infiltration of porous metal skeletons produced by powder metallurgy methods, including 3D printing technologies, with an aluminum-based melt under a pressure gradient is studied. The densification of compacts made of iron powder with the addition of various blowing additives is examined. The minimum pressures at which a porosity of 35–40% is reached is 150–200 MPa. The use of metal iron waste in the form of shavings allowed the formation of porous skeletons at a lower pressure of 100 MPa. The minimum pore size (400 µm) that ensures complete filling of the porous skeleton with the aluminum-based melt heated to a temperature of 760–780 ºC under a pressure gradient was established. The potential production of composites in the iron–aluminum system without the formation of chemical compounds is shown. At the same time, a thin discrete layer with a thickness of 5–10 µm is observed at the interface between iron and aluminum, where the iron skeleton was 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 kinetics of the process: the components do not have time to react with each other for several seconds. The effect exerted by the type of porous skeletal struc-ture on the compressive strain of the iron–aluminum composites is established. The greatest tensile strength (~400 MPa) is shown by the samples produced from 3D skeletons. The diagram for the samples produced from 3D skeletons shows two bends: one 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 is observed for samples with shavings-based skeletons (115.2 MPa), which is associated with a high contact surface area of the shavings particles that are randomly intertwined. Accordingly, the lowest characteristics are shown by the samples with skeletons consisting of powder particles with the minimum contact area.