Friction and Wear of Composite Material Based on Al–Mg Alloy Modified by Iron Powder via Friction Stir Processing

This work is dedicated to the study of tribological behavior of composite materials obtained by friction stir processing (FSP) from AA5056 aluminum–magnesium alloy with addition of iron under dry sliding friction. For the tests, four different types of samples were obtained by FSP, differing in their iron powder content, namely 0, 5, 10, and 15 vol %. For each type of composite, four passes of FSP were performed to achieve a uniform distribution of the iron powder throughout the stir zone. Sliding tests were conducted using the pin-on-disc method against a counter-body made of stainless steel containing 12–14% chromium (AISI 420). Increasing the Fe powder content leads to a decrease in the average coefficient of friction by approximately 10–15%, as well as a reduction in wear by approximately 20%. The study of worn surfaces showed that with an increase in the amount of iron powder added during FSP, the wear mechanism changes from adhesive to abrasive. Homogeneous distribution of intermetallic compound (IMC) particles of Al₆Fe and Al₁₃Fe₄ in-situ synthesized during FSP made it possible to increase the wear resistance of the composites compared to the base alloy without iron additives. A mechanically mixed layer consisting of a deformed matrix mixed with fragmented and oxidized IMCs was formed on the worn surfaces of all the studied composites and served as protection against adhesive wear and performed the function of a wear-resistant antifriction coating.