Microstructural damage during electrical discharge machining of a high silicon aluminum alloy for space applications

Aluminum alloys with 40 to 50 wt.% silicon content are potential material candidates for the manufacturing of satellite components. These materials have excellent thermal and mechanical stabilities, but machining complex components from these alloys is facing many challenges. The present study was performed on an aluminum-high silicon alloy (50–50 wt.%) with the main aim of investigating the evolution of the microstructure with particular attention to surface and subsurface damage as a result of Electrical Discharge Machining (EDM). For this purpose, the microstructure was characterized by optical and Scanning Electron Microscopes (SEM) as well as Energy Dispersive Spectroscopy (EDS) of the machined samples. The results show the existence of melted and re-solidified zone with much finer silicon particles located in a zone on the top of the machined surface where cracks were also observed. Moreover, SEM examinations showed that the cracking damage concern the primary silicon particles. Possible mechanisms, such as the thermal shock produced by rapid cooling rate of the primary silicon particles and the presence of porosities, formed during the manufacturing process, are discussed.