EDM surface effects on the fatigue strength of a 15 vol/100 SiC_p/Al metal matrix composite material

摘要

The effects of electrical discharge machining (EDM) on the surIhce quality and subsequent performance of a 15 vol/100 SiC particulate reinforced A356 Al under monotonic and fatigue loading conditions are investigated. Surface and subsurface conditions after EDM surface sparking of the material were compared with the same material after careful surface polishing. Tensile tests were performed on the as-received material and the EDM surface sparked material to ascertain effects of EDM processing on basic monotonic properties. High cycle constant stress amplitude fatigue tests were conducted on the polished material and on the sparked material, and fractographic analysis was performed to study the mechanisms of fatigue fracture. EDM sparking was found to dramatically increase surface roughness and cause slight subsurface softening in the microstructure below the outer recast layer. Fatigue strength is notably reduced by EDM processing, with greater degradation resulting from higher material removal rates (MRRs).