Cutting mechanisms and surface features of WED machined metal matrix composites

Metal matrix composites are manufactured in a variety of grades and forms, but machining is usually necessary to obtain finished engineering components. The presence of the hard reinforcing ceramic makes these materials difficult for conventional machining. Wire electro discharge machining (WEDM) is used for the processing of heat-treated high-quality alloys or for the machining of complex shapes in advanced materials. This paper describes WEDM tests performed under one roughing and two finishing conditions on two composites, SiC/2009Al alloy with 15% whiskers and with 20% particles reinforcement. Some roughed and some finished surfaces were glass-bead peened. To understand the reinforcement and the behaviour of the matrix during the machining of both composites, the machined surfaces, their sections and profiles were examined by scanning electron microscopy, and energy dispersive semi-quantitative analyses of X-rays were also carried out. The surface roughness for the process parameters used are indicated. (C) 1997 Elsevier Science S.A.