Multi-Response Optimization of Electrochemical Machining of Al-Si/B4C Composites Using RSM

Multi-Response Optimization of Electrochemical Machining of Al-Si/B4C Composites Using RSM

Sadineni Rama Rao (VISIT Engineering College, Tadepalligudem, Andhra Pradesh, India) and G. Padmanabhan (S.V. University College of Engineering, Tirupati, Andhra Pradesh, India)
DOI: 10.4018/ijmmme.2013070103
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Abstract

The present work reports the electrochemical machining (ECM) of the aluminium-silicon alloy/boron carbide (Al-Si /B4C) composites, fabricated by stir casting process with different weight % of B4C particles. The influence of four machining parameters including applied voltage, electrode feed rate, electrolyte concentration and percentage of reinforcement on the responses surface roughness (SR) and radial over cut (ROC) were investigated. The process parameters are optimized based on the response surface methodology (RSM) and the optimum values for minimizing surface roughness and radial over cut are voltage 15.25 V, feed rate 1.0 mm/min, electrolyte concentration 13.56g/lit and percentage of reinforcement 7.36 wt%. The quality of the machined surfaces is studied by using scanning electron microscopic (SEM) images. The surface plots are generated to study the effect of process parameters and their interaction on the surface roughness and radial over cut, for the machined Al-Si/B4C composites.
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Introduction

Metal matrix composites (MMC) have emerged as an important class of materials, which are increasingly being utilized in recent years. Among the various types of MMC, aluminium-based composites have been found in various engineering applications such as the aerospace, defense, biomedical and automobile industries because of their inherent properties like high strength to weight ratio, low wear rate etc. Some of the typical applications are bearings, automobile pistons, cylinder liners, piston rings, connecting rods, sliding electrical contacts, turbo charger impellers, space structures, etc. (Ding et al., 2005). High hardness silicon carbide (SiC) or aluminium oxide (Al2O3) or boron carbide (B4C) particles are commonly used to reinforce aluminium alloys, but the full application of such MMC is, however, cost sensitive because of high machining cost (Hung et al., 1995). The machinability of MMC has received considerable attention because of high tool wear associated with machining. The turning, milling, machining, or threading of MMC reinforced with Al2O3 particles are extremely difficult due to their extreme abrasive properties (Sahin et al., 2002). Studies on the machinability of light alloy composites reinforced with Al2O3/SiC fibers/particles (Tomac et al., 1992; Cronjager et al., 1992) indicate poor machinability due to the abrasive wear of tools. Moreover, the quality of the machined surface also deteriorates with tool wear (Chandrasekaran et al., 1997). Due to the above limitations several researchers have studied the machining of MMC through non-traditional machining processes.

Mathematical models of the material removal rate, tool wear rate and surface roughness were developed by response surface methodology to predict the influences of machining parameters on response factors during electric discharge machining of AA6061.wt.10% B4Cp(Thangadurai, 2012). The influence of process parameters like peak current, flushing pressure and pulse on time on material removal rate, surface roughness and tool wear rate in electric discharge machining of aluminium-fly ash-graphite hybrid metal matrix composites was investigated by Prasad et al. (2011).

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