Production characterization and friction stir welding of Al TiB2 metal matrix composites

Abstract

Metal matrix composites (MMC) have been the subject of scientific investigation and applied research for about two decades but only in the past few years these advanced materials became realistic candidates for critical structural applications in industrial sectors. Ceramic materials generally used to reinforce aluminum alloys include the carbides (e.g. SiC, TiC), borides (TiB2, ZrB2), nitrides (AlN, Si3N4) and oxides (Al2O3, SiO2). Among these reinforcing particulates, titanium diboride (TiB2) is particularly attractive because it exhibits high elastic modulus and hardness, high melting point, and good thermal stability. However, one of the main limitations for the industrial application of the particulate reinforced aluminium matrix composites is the difficulty in using conventional fusion welding methods because of the resulting joint defects due to undesirable reactions between the reinforcement particles and liquid aluminium in the fusion zone. Friction stir welding (FSW), a solid state joining method, is the most preferred process for joining particulate reinforced aluminium matrix composites since the energy input and distortion are appreciably lower than those in fusion welding techniques. Box Behnken design of experiments and analysis of variance (ANOVA) were employed to investigate the influence of FSW process parameters on tensile strength and percentage ductility. Mechanical characterization studies revealed that the tensile strength of the composites registered an increase with addition of higher percentages of the reinforcing particulate. This investigation concludes that an Al6061based MMC with a particulate presence of up to 10% could be manufactured through the in-situ reactive processing route employing manual stir casting method and that sound joints of AlTiB2 MMCs could be produced through the friction stir welding technique by appropriately controlling the process parameters. newline newline newline