Investigation on machining performance of powder mixed electric discharge machining of aa7050 hybrid composites

Abstract

In this research work, AA7050 aluminum alloy was reinforced with newlineSilicon Carbide and Aluminium Oxide particle of size 5and#956;m through liquid stir newlinecasting route. The wettability of the composites was attained by adding newlinemagnesium powder as flux. The reinforced particles are preheated at 250and#7506;C newlinebefore adding to the melt. Uniform distribution of composites was confirmed newlinethrough SEM with EDS mapping and the results revealed that the particles are newlinehomogeneously distributed over the matrix material. The density was newlinedetermined through liquid immersion technique and compared with newlineexperimentally calculated value to compute the void fraction. The void newlinefraction was within the prescribed range, according to the findings. newlineDie Sink electric discharge machining were performed on the newlinecomposites by varying powder concentration, current and pulse on time. newlinesilicon carbide, aluminium oxide and graphite are the distinct powders mixed newlinewith the dielectric fluid to enhance the machining performance. Taguchi newlineorthogonal approach was used to design the experimental runs whereas newlinematerial removal rate, tool wear ratio, machined surface hardness and surface newlineroughness were recorded as response. The results revealed that MRR newlineincreases with the addition of particles in the dielectric medium owing to the newlinebridging effect. The composites machined under PMEDM condition showed newlineleast Ra value owing to the increase in spark gap. The spark gap increment newlinefacilitates the complete flushing of machined debris which eliminates the newlineformation of remelted layer on the surface. The surface topography showed newlineremelted layer, micro pits, craters and pock marks and some of the above newlinementioned features were eliminated under PMEDM condition. Owing to the newlineelimination of the remelted layer the PMEDM machined surface offers least newlinemachined surface hardness compared to that of the EDM machined surface. newlineThe addition of powder has trivial impact on TWR, as maximum newlineimprovement of 5% reduction in TWR was achieved newline newline