Investigation of the Microstructure and Dry-Sliding Wear Behavior of Co Containing Al-Si-Fe Scrap Alloy

Abstract

This study investigates the influence of cobalt (Co) addition on the microstructural and wear properties of an aluminum (Al) scrap alloy containing high iron (Fe) impurity content (3%). Microstructural analysis using scanning electron microscopy and optical microscopy confirmed the presence of Co in Fe-rich intermetallics. Upon increasing the Co concentration, β-Al5FeSi phase was seen to be refined without significant morphological modifications. Furthermore, Co addition promoted the formation of a new quaternary phase Al32Si7Fe4Co phase, which was finely distributed throughout the microstructure and acts as a tribo-layer in the Al scrap alloy, offering enhanced wear resistance and improved stability against wear. Standard EN-31 steel disk with compositions chromium (Cr)-1.6%, manganese (Mn)-0.75%, silicon (Si)-0.35%, and carbon (C)-0.9% was used for the wear test. Microhardness and wear properties were evaluated for both the as-cast and heat-treated alloys, with the as-cast samples exhibiting superior wear resistance and a lower coefficient of friction compared to the T6 heat-treated samples. Addition of Co showed refinement in the β-Fe rich intermetallics over the morphological modifications. Similarly, Co addition enhanced the hardness and wear resistance in the as cast alloys. This work provides a detailed analysis contributing significant understandings into the wear mechanisms and potential applications of Co modified recycled Al in various industrial sectors.