Abstract
The aluminum alloy AA6061-4wt.% boron carbide (B4C) particulate metal matrix composites were fabricated by the stir casting method. The die-sinker electric discharge machining was performed to make the rectangular mini channels on these composites. The full factorial experimental design that consists of three input conditions, the current ( I), discharge duration ( T-on), and discharge idle time ( T-off) at three levels each (33 = 27 total runs), was used for experimentation. The volume, V, the taper, θ (along with the depth), the lateral overcut (along the width), and the difference in depth, Δ d (between total depth and depth up to the tapered profile) at entrance and exit cross-sectional profiles of the channel were considered as output responses. The θ, lateral overcut, and Δ d were calculated from the entrance and exit profiles which were obtained by extracting the data points of each channel with the help of an optical profile projector. The computer-aided geometric model was developed to estimate the volume. A set of optimum electric discharge machining parameter levels were identified for maximum V and a minimum of θ, lateral overcut, and Δ d. Analysis of variance was performed to identify the significant parameter and the contribution toward output responses. Results showed that the volume was found to be maximum at higher I (8 A) and lower T-On (25 µs) conditions. The taper was found to decrease with the increase in current but both lateral overcut and Δ d increased. Both I and T-On are found to be the significant parameters affecting both V and Δ d, whereas current is for θ and lateral overcut. In some cases, it was observed that there is a considerable difference in the θ and the lateral overcut values in the entrance and exit portions for the same channel. It is because of the randomly dispersed B4C particles which alter the material removal mechanism.
Highlights
Machining of micro/mini channel profiles on various work materials has gained research interest among several groups because of higher heat dissipation capability by allowing the cooling fluids to flow through them.[1,2] Various conventional and non-conventional machining methods were reported and are being practiced to make these channels
The reason is at the higher discharge current, the amount of heat energy available due to generated plasma is sufficient enough to melt or even evaporate the work specimen
During the shorter discharge duration time the heat energy density is high because of the insufficient time to spread the plasma over the larger area
Summary
Machining of micro/mini channel profiles on various work materials has gained research interest among several groups because of higher heat dissipation capability by allowing the cooling fluids to flow through them.[1,2] Various conventional and non-conventional machining methods were reported and are being practiced to make these channels. Haghbin et al.[3] used abrasive water-jet micro-milling to machine the channels on 316L stainless steel and aluminum alloy AA6061T6. Karthikeyan et al.[5] employed the microelectric discharge milling of EN 24 steel to machine the microchannels. Salimi et al.[7] used a friction stir-based process to fabricate the cooling channel profiles on aluminum AA6061T6. Gudipudi et al.[8,9] employed sinker-electric discharge machining (EDM) to make rectangular channels on AA6061-B4C composites. These composites in which a certain amount of reinforcement (RF) particles are incorporated into the base metal matrix showed improved performance in thermal management
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