Effect of tool pin geometry and cooling-assisted FSP on mechanical and tribological behavior of AA5083/SiC surface composites

Abstract

The study examines the production of AA5083/SiC surface composites produced through friction stir processing using 6 vol.% SiC nanoparticles and five tool-pin profiles (tapered cylindrical, threaded cylindrical, taper threaded cylindrical, square and hexagonal) under dry and water-jet cooling (25°C ± 2°C) conditions. An exhaustive temperature, micro-structural, micro-hardness, tensile and wear profiling was conducted to evaluate the effects of the tool-profile and cooling-effect during process. The highest temperature at which the processing took place dropped to 214.58°C with cooling compared to 416.17°C during dry conditions, which is an indication that it had proper thermal control. The cooling cylindrical tapered tool attained a refinement of about 83% in the grains; the composites showed a 26.6% greater micro-hardness of the base alloy. The maximum tensile strength of 165.74 MPa was observed with the square tool under cooling, against 102.56 MPa for the base alloy, with moderate elongation retention. Fractographic data showed dimples on the base alloy ductile and finer dimples with craters on the composites, which were signs of a strong interphase between SiC-matrix and the composites. Wear testing showed that specific wear rate was reduced by 45.8% (dry) and 64.1%(cooling), which is consistent with the synergetic behaviour of reinforcement and temperature control on the surface integrity. The observations of scanning electron microscopy established a consistent SiC dispersion, grains and smoother worn surfaces with little debris thus confirming the fact that the developed composites showed better mechanical and tribological performance.