FRICTION. STIR PROCESSING OF CAST Al-Si ALLOYS FOR IMPROVED MECHANICAL AND TRIBOLOGICAL PERFORMANCE

Abstract

Friction stir process has the capability for improving the mechanical and tribological performance of the cast hypereutectic Al-17% Si alloy locally. In this current study, FSP was carried out in two phases: - (I). Friction stir processing of cast Al-17% Si alloy and (2). Composite fabricated using FSP. In first phases the effect of process parameter such as transverse speed (26, 40, and 60) mm/mm, at fixed rotational speed 664 rpm on the mechanical and tribological performance of the cast Al-Si alloy was studied and in second phase, composite reinforced with using Zn! MoS2 powder in cast Al-17%Si alloy were developed at tool rotational speed of 20 rnin/min and tool transverse speed was 664 rpm using friction stir processing. Friction stir processed of' cast Al-Si alloys were characterized with optical microscope, FFSFM. hardness, tensile and F[)X. Composite surfaces were studied using optical microscope, FESEM, FI)X, hardness, tensile and wear. The microstructure of cast alloy was improved in terms of refinement of' cutectic and primary Si particles, uniform distribution of Si, reduction in porosity. The hardness was found to be improved after FSP and in the composites, while tensile properties were greatly improved and the tensile elongation of FSPed samples increased from < 2 % to about 9 %. In case of base material the range of variation of coefficient of friction with sliding distance was found wider as 0.2 to 0.6, but in case of composite fabricated with MoS2, the coefficient of friction was narrower in the range of 0.25 to 0.45. MoS2 reinforced composite showed superior wear resistance than that Zn reinforced composite and base material.