Multiobjective Optimization of EDM Parameters for Rice Husk Ash/Cu/Mg-Reinforced Hybrid Al-0.7Fe-0.6Si-0.375Cr-0.25Zn Metal Matrix Nanocomposites for Engineering Applications: Fabrication and Morphological Analysis

Abstract

The advanced class of Al/(RHA+Mg+Cu) hybrid metal matrix nanocomposites (MMNCs) has exhibited superior physical, and mechanical properties with superior wettability and chemical compatibility. This work has also been reported on the machining and multiobjective optimization of process variables for the machining of Al/(RHA+Mg+Cu) hybrid MMNCs on EDM using L27 Taguchi’s orthogonal array integrated with Grey rational analysis (GRA). The primarily target goal of this study is to produce nanocomposite having better properties with minimal production cost, with the use of reinforcement rice husk ash (RHA). RHA is utilized in the base matrix of Al 6061 at wt.% of 6, 8, and 10. On the other hand, the elements such as Cu and Mg are placed fixed, i.e., 3 wt.% and 1 wt.%, respectively. The hardness, tensile strength, and impact strength of the nanocomposites increased with the maximum increment of 35.11%, 15.76%, and 16.67%, respectively, as compared to neat composite. Further, the purpose of this investigation was to determine the effect of various factors such as the percentage of RHA in the workpiece electrode (W), the discharge current (I), the voltage (V), the duty factor (τ), the pulse-on time (Ton), and the flushing pressure (P) on the material removal rate (MRR), the surface roughness (SR), and the tool wear rate (TWR) during the machining of hybrid nanocomposites using Taguchi’s approach. The results revealed that MRR decreased with increasing the RHA content in the workpiece which can be reasoned to isolating nature of the RHA. It clearly shows that SR has decreased with an addition of RHA content from 6 wt.% to 8 wt.% in workpiece, but it slightly increased by further addition of RHA from 8 wt.% to 10 wt.%. SR has decreased with an increase in duty factor while performing EDM trials with the copper electrode, but it slightly increases with a further increase in duty factor. By the increase in pulse-on time, spark energy also increases also leading to the formation of craters. Therefore, SR has increased with an increase in pulse-on time. The TWR has increased with an increase in RHA content in the workpiece, because of the existence of hard reinforcements on the matrix which causes larger wear in the tool. Analysis of SEM micrographs showed the presence of voids, shallow and deep craters, and black voids on the machined surface of the fabricated hybrid nanocomposites. As calculated using the response graph for GRG, confirmation tests for optimal parametric setting show improvement over initial parametric setting of machining parameters. The mean of optimal MRR, SR, and TWR is estimated at the significant level of machining factors at A1B3C3D2E3F1, A2B1C1D2E1F3, and A1B1C1D1E1F3, respectively.