A study on geometrical features of electric discharge machined channels on AA6061-4%BC composites

Abstract

The aluminum alloy AA6061-4wt.% boron carbide (B 4 C) 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 (3 3 = 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 B 4 C particles which alter the material removal mechanism.