Experimental Evaluation of Mechanical and Tribological Properties of Segregated Al-Mg-Si Alloy Filled with Alumina and Silicon Carbide through Different Types of Casting Molds

Abstract

A 6061 aluminum alloy has almost 0.8–1.2 wt.% Mg and 0.4–0.8 wt.% Si content. These two components, along with other alloying elements, therefore, were characterized by high mechanical and abrasive strength. The aims of the present work were to understand the effect of different types of cooling rates through different molds materials and to investigate the effect of casting with ceramic additives on segregation of the aluminum alloy itself as a composite material forum. Therefore, a series of mechanical tests were conducted, such as compression test, Vickers hardness, and pin-on-disc wear test. The samples were cast at 650 °C and in electric furnaces for 2 h to ensure that the metal achieved adequate homogeneity and temperature. Then, abrasive macroparticles of Al2O3 and Sic with a size close to 40–60 µm were used. The particles were poured under constant stirring for 1 min. Then, they were cast in two types of molds: steel and graphite. The cast specimens were obtained as a reference without particles and with 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 8 wt.%. The thermal effect and the heat due to conduction and radiation were calculated. The maximum compressive strength was found to increase by ≈21% with SiCp casted in graphite molds, and HV was found to increase by ≈29% with SiC casted in graphite molds. The same was found for wear resistance, which became good with SiC casted in graphite molds, and it was generally found that the cooling rate through the mold weakened the alloy due to the segregation effect. The presence of tough particulate through the aluminum matrix barrier created a number of loads. Additionally, the high specific heat of graphite, which plays a dominant role in the slaw cooling rate of casting, led to grain enlargement, whereas the higher cooling rate of steel led to grain refinement. These concepts are the main rules of heat treatments through the casting process itself, and they save time and effort.