Abstract
Abstract In this paper, Rheo-Die Cast (RDC) Al-Si alloy with 7.5 wt % Si and 0.3 wt %Mg and Metal Matrix Composites (MMC’s) of RDC Al-Si composites with 5 to 20 vol. % of SiCp were produced by an in-house fabricated RDC machine. Microstructure and wear behavior of both RDC alloy and composites were investigated. Results indicated that the RDC samples have significantly refined microstructure with fine and uniform non-dendritic grains resulting increased hardness and enhanced wear resistance. Wear resistance is three times higher for sample with 20% SiCp than those without SiCp additions. Surfaces of wear test samples were investigated by SEM to study the effect of both grain structure and SiCp particulates on the wear mechanism. It was also observed that reinforced RDC samples showed improved hardness and wear resistance due to the presence of SiCp in the matrix of non-dendritic grains, obtained without modification treatment.
Highlights
Aluminum-silicon alloy castings with a wide range of Si content have been extensively used in aerospace and automotive industry for the last two decades due to their high strength, low density, good castability, good corrosion resistance and weldability[1,2]
This modification in the microstructure of RDC alloy confirms that the RDC equipment is capable of producing sufficient quantities of slurry particles, which aids in converting the microstructure from dendrite grains to non-dendritic or fibrous grains in Al-Si alloys
In-house designed and fabricated Rheo-DieCasting (RDC) equipment was successfully used for development both unreinforced and reinforced SiCp particulate RDC Al-7.5 wt % Si-0.3 wt % Mg alloys under semisolid conditions
Summary
Aluminum-silicon alloy castings with a wide range of Si content have been extensively used in aerospace and automotive industry for the last two decades due to their high strength, low density, good castability, good corrosion resistance and weldability[1,2]. Paes and Zoqui[8] studied the microstructure of Al-Si-Mg alloys in the semisolid condition and reported high solid fractions in semisolid condition in Al-Si-Mg alloys with 4wt % to 7 wt % Si and 0.5wt % and 1.0 wt% Mg respectively. They proposed a Rheo-cast Quality Index (RQI) for the Al-Si-Mg alloys to examine the thixo-formability of the modified aluminum alloys. A high RQI value indicated a good thixo-formability of the modified alloys This value is related to low silicon content in the aluminium alloy. Birol[16] studied the microstructure of semi-solid processed A356 die-casting alloy and found that the solid fraction linearly increased in semi-solid temperature range
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