Mechanical and Wear Properties of Friction Stir Welded 0–6Wt% nAl₂O₃ Reinforced Al-13Wt%Si Composites

Abstract

Friction Stir Welding (FSW) of an Al-13%Si alloy matrix reinforced with 0, 3 and 6 wt% Al2O3 nanoparticles (nAl2O3) is performed and the optical microstructures, tensile strength, hardness and sliding wear properties of friction stir welded joints are investigated and compared to those of base materials. Four different zones of distinct appearances were observed during FSW, which exhibited altered microstructures in the nugget zone (NZ), thermo mechanically affected zone (TMAZ), heat affected zone (HAZ), and base material zone (BMZ). The ultimate tensile strength of the base materials and their welded joints were found to be increasing with increased wt% of nano-alumina reinforcements. High joint efficiency of 89-97% was achieved in FSW. Hardness and wear resistance of friction stir welded joints were found to be better than those of the base materials. KEYWORDS:Friction stir welding, Metal matrix composite, Mechanical properties, Al-Si alloy, Alumina, Wear IntroductionVarious hard micro/nanoscale ceramic particle reinforced aluminium matrix composites are among the most widely studied metal matrix composite materials owing to their excellent material properties such as high specific strength and stiffness, low density, low thermal expansion and enhanced creep and wear resistance. The widespread usage of these metal matrix composites with the advancements of various ceramic particles is severely limited due to inadequate and inefficient secondary processing or manufacturing techniques such as machining and welding. The Welding Institute (TWI) UK [1] patented a solid-state joining method "friction stir welding" which has been used widely to produce high quality welds in many materials like aluminium, nickel, magnesium, titanium and steel for applications in automobiles Friction stir welding has an advantage over fusion welding of metal matrix composites owing to the absence of any kind of segregation and/or reaction to the reinforcements, hot cracking and porosity during the solid phase welding process. Al-Si alloy is one of the most popular materials for aerospace, automobile, and marine industries due to its high fluidity and castability, low density, high specific strength and good corrosion properties [13,14]. Silicon is known for reducing thermal expansion and increasing wear and corrosion resistance of the alloy [15]. Ceramic reinforcements further improve the wear resistance properties of Al-Si alloys. Absence of melting in FSW diminishes the probability of defect formation and recovers the mechanical properties which enable FSW a capable joining method for metal matrix composites (MMCs). Several studies have been performed on FSW of micro-sized alumina Unauthenticated Download Date | 5/11/18 1:43 PM

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