Experimental Investigation on the Synthesis of Al5086-GRN-ηSiC Hybrid Surface Composite Using Additive Powder Fed Friction Stir Processing

SYNTHESIS OF Al5086-GRN-ηSiC HYBRID COMPOSITE

Abstract

In the current research work, graphene (GRN) and nano-silicon carbide (SiC) reinforced Al5086-alloy based hybrid surface composites has been developed using a unique surface engineering technique called additive-powder-fed friction stir processing (APF-FSP) process. Herein, the mechanical exfoliation of graphite into GRN has been carried out using APF-FSP process to improve the microstructural and mechanical properties. The microstructure, morphology, and mechanical properties of as-synthesized hybrid Al5086-GRN-ηSiC surface composite has been investigated. Microscopic analysis has been conducted to scientifically ascertain the grain size, crystal structure and surface morphology of APF-FSP zone. The mechanical properties such as hardness and elastic modulus have also been evaluated using nanoindentation and micro-hardness technique. Nano-indentation and micro-pillar testing techniques have been used to assess mechanical properties in terms of hardness, elastic modulus, and compressive strength of as-developed hybrid Al5086-GRN-ηSiC surface composite. The best optimal condition to obtain the defect free structure is 1800 RPM rotational speed and 40 mm/min transverse speed with trapezoidal shape tool pin geometry. The microstructure and morphological examination reveal that the grain size of Al-matrix gets refined from 30 µm to ~8 µm and reinforcements (GRN/ ηSiC) are uniformly distributed in the matrix, which is expected to improve the mechanical properties. The SEM and TEM morphology analysis show that the diphasic nano-mixture cluster of ηSiC and GRN in the range (100-200 nm) have been formed and GRP co-exist in multi-layer of atoms in Al-matrix owing to mechanical exfoliation of graphite. The highest hardness (145 HV_0.3) and tensile strength (385  MPa) have been obtained. Overall, findings of this work conclude that APF-FSP offers up new possibilities for fabricating functionalized surface composites with improves mechanical properties for aerospace and automobile industries.