Investigation of microstructural and wear behavior of Al6061 surface composites fabricated by friction stir process using Taguchi approach

The surface composites of aluminum alloys have a higher scope of applications encountering surface interactions in the aerospace, automobile, and other industries compared to the base aluminum alloys. The friction stir process (FSP) is recently the preferred method to prepare aluminum-based surface composites due to its capability to produce improved physical properties and refined microstructure at the surface. The study examines the Al6061 alloy-based surface composite fabricated by FSP for their wear behavior and microstructure. In this study, the Al6061 alloy-based hybrid surface composites are prepared with varying weight% of copper and graphite microparticles mixture as reinforcement by FSP with two tools having unique pin profiles, i.e., threaded cylindrical and plain cylindrical. These prepared composites are investigated for the dry sliding wear test on a pin-on-disc test set-up. The experiments are designed using the L9 orthogonal array and analyzed by the Taguchi approach to obtain the influence of disc speed, load, and reinforcement weight% on wear rate. The significant parameters influencing the wear rate of the samples tested are obtained using ANOVA. Later the effects of the friction stir process and the wear tests on the microstructure of the workpieces are investigated using FE-SEM/EDS tests. It is concluded that the decrease in wear rate with the rise in reinforcement weight% (Cu + graphite) from 2% to 6%. The load has the maximum effect on the wear rate for the samples prepared by threaded cylindrical FSP tool pin profile, while reinforcement weight% affects significantly the wear rate of the samples prepared by FSP with plain cylindrical pin profile tool.

Influence of Fly Ash and Emery based particulate reinforced AA7075 surface composite processed through friction stir processing

The novel friction stir technology is adopted in modern automotive industries to meet the desired properties like hardness, impact toughness and tribological behaviour over the conventional techniques like stir casting, compo casting, squeeze casting, electroplating and infiltration methods. AA7075 surface composites fabricated with different volume fractions of fly ash and emery particles is said to enhance the aforementioned properties. The composites are processed through friction stir process (rotational speed −1200 rpm, transverse speed – 56 mm/min, tool tilt angle – 2 °). During characterization, the Microstructural examination of surface composites depicts fine and homogenous distribution of reinforcements in the friction stir process region owing to severe plastic deformation and dynamic recrystallization process. Substantially, good interface is formed between the reinforcement particulates and base substrate. Inclusion of Fe3O4, Al2O3 and SiO2 constituents through fly ash and emery reinforcements associated with the homogenous dispersion strengthening mechanism favours for the superior hardness of surface hybrid composite specimen 50E50FA. Decremented grain size and load bearing capacity of the reinforcements is beneficial for the crack propagation resistance that enhances the impact toughness behaviour (17.4 J/cm2) of the same specimen. Wear rate of the specimens are evaluated through pin on disc tribometer. The decrease in the wear rate of hard specimen 50E50FA is observed due to the reduced contact area between its surface and counter disc. The morphology of worn specimens using SEM analysis shows the combined abrasive and adhesive wear as the worn mechanism.

Mechanical and microstructural characterization of Ti-SiC reinforced AA5083 surface composites fabricated via friction stir process

A mixture of Titanium and silicon-carbide powders was embedded in the AA5083 matrix by Friction Stir Processing (FSP). Experiments were performed as per Taguchi L8 orthogonal array, and the effect of reinforcement on hot strength (at 100oC), processed zone (PZ) geometry, and microstructure were investigated. The effect of PZ geometry on the surface properties was also analyzed. The effect of heating the tensile test specimens to 540ºC on the strength at 100oC was also separately investigated. It was observed that surface hardness was significantly enhanced by FSP, and the highest mean hardness of 90.4 HV was observed. Furthermore, it was observed that the surface properties also significantly depend on PZ geometry. From experimental results, it was found that the specimens with the lowest width to depth ratio bears the highest hardness and vice versa. A clear effect of parameters was evident on the geometry of processed zones with a deep bowl, and shallow cup-shaped zones were formed with smaller and larger shoulder diameters, respectively. The samples were processed at 355 rpm, 63 mm/min, 17 mm shoulder, and 355 rpm, 80 mm/min. The 20 mm shoulder showed high tensile strength 292 MPa and 294 Mpa, respectively. The strength of these samples did not reduce much even after heating to 540oC.

EFFECT OF DEPOSITION TECHNIQUES OF REINFORCEMENT DURING FABRICATION OF AL-BASED SURFACE HYBRID MATRIX METAL MATRIX COMPOSITE

Several deposition methods have been proposed for pre-deposition of reinforcement particle for preparation of surface metal matrix composite by Friction Stir Process. The method, which will effectively and homogeneously spread the reinforcement within processed zone, will be considered as best possible method.Homogeneous volumetric metal matrix composites can be fabricated by conventional casting and modified stir casting methods. Friction stir process (FSP) can be used as one of the best technique to fabricate surface modified metal matrix composites. In this research article, silicon carbide and graphite powder are used as reinforced materials and AA6061 is used as parent metal matrix material. FSP which is a versatile surface composite preparation technique is applied for fabrication of surface composite. Herein, single channel, multi-channel and perforated holes methods have been utilized for reinforcement deposition. As per the results, perforated blind holes method is reported as best method of pre deposition of powders. Finally, array of holes for pre-deposition of reinforcement powder improves approx 25% in ultimate tensile strength , 40% in micro-hardness and appreciable grain refinement are observed in metal matrix composite processed by FSP as compared to as received alloy.