INVESTIGATION OF JOINING OF ALUMINIUM BASED METAL MATRIX COMPOSITES USING FRICTION STIR WELDING

Abstract

Current dissertation work discusses the suitability of mixed salt route using stir casting method to fabricate Al-4.5%Cu/2.5wt.% TiB2 in situ metal matrix composite. Two salts: KBF4 and K2TiF6, one containing boron unit and the other containing titanium unit, were mixed in the molten alloy to prepare the composite. The prepared aforementioned composite was then friction stir butt welded. A bimetallic tool with flame hardened titanium probe with varying shoulder geometries was used to join the composite. Tool rotational speed and welding speed were varied along with the tool geometry and their effects on the tensile strength, percentage elongation and micro-hardness of the welds were studied. The reinforcement phase was refined and redistributed uniformly in the stir zone due to the stirring action of the probe. Although an intermetallic phase CuAl2O4 was formed in the stir zone, the stir zone exhibited ductile nature. To predict the mechanical responses of the weld, a mathematical model based on Response Surface Methodology (RSM) was developed which predicted the response satisfactorily. Through this model, it was determined that the tool type was the most significant variable in determining the mechanical response of friction stir butt welded Al-4.5%Cu/2.5wt.% TiB2 in situ metal matrix composite