Development of Al-Fe3Al Composites by Powder Metallurgy Route

Abstract

Aluminium based MMCs are one of the most prominent materials due to their low density, high specific strength and stiffness and increased fatigue resistance which make them suitable for various wear and structural applications in various aerospace and automotive industries. Aluminium (Al) is widely used due to its excellent properties such as low density high thermal and electrical conductivity. However, Al has poor wear resistance behaviour, low hardness and poor fatigue properties. This is why Al is very often reinforced with hard materials like carbides, borides, nitrides, oxides and intermetallics. Rising interests in intermetallic compounds is connected with their high strength, corrosion resistance and wear resistance. Among the several intermetallic compounds available iron aluminide (Fe3Al) has been frequently considered for high-temperature structural applications because of their unique physical and mechanical properties. Fe3Al intermetallic compound has a high melting point, high hardness, low density and good oxidation and corrosion resistance. In the present work, an attempt has been made to study the effect of addition of Fe3Al as reinforcement in Al metal matrix composites. Here, in the present research work Al-10, 20, 30 vol. % Fe3Al composites have been developed by powder metallurgy route and their microstructure, hardness and wear properties have been investigated. In the present research work both as-received Fe3Al and Fe3Al developed by 40 h of mechanical alloying (MA) of Fe75Al25 powder followed by heat treatment at 1100oC for a period of 2 h in Ar atmosphere has been used as reinforcement. Nanocrystalline Al developed by milling Al powder for a period of 20 h has been used as the matrix for all the Al-Fe3Al composites developed in this study. The milled powders were analyzed using x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX), high resolution transmission electron microscope (HRTEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The 20 h milled nanocrystalline Al was mixed with both the as-received Fe3Al powder and the Fe3Al powder synthesized by MA in different vol. % and compacted under a uniaxial load of 222 MPa and sintered at 500oC for a period of 2 h in Ar atmosphere. The microstructure of the various Al-Fe3Al sintered composites was analyzed using optical microscope, SEM and EDX. The relative density of the various sintered composites was determined by the Archimedes’ principle. Dry sliding wear test of the various sintered composites was done on a ball-on plate tribometer to determine the wear behaviour of the composites. The hardness of the composites was determined using a Vickers microhardness tester. It was found that both the hardness and the wear resisiatnce of the various Al-Fe3Al sintered composites increased with the increase in Fe3Al content.