An analysis of the discharge mechanism in electrochemical discharge machining of particulate reinforced metal matrix composites

摘要

An analysis of the discharge mechanism in electrochemical discharge machining (ECDM) of a particulate reinforced metal matrix composite was undertaken, and a model to reveal the electric field acting on a hydrogen bubble in ECDM process has been established. The model was found capable of predicting the position of the maximum field strength on the bubble surface as well as the critical breakdown voltage for spark initiation, for a given processing condition. A set of experiments was performed to verify the model and the experimental results agreed well with the predicted values. The experimental results also showed that an increase in current, duty cycle, pulse duration or electrolyte concentration would promote the occurrence of arcing action in ECDM. Moreover, by studying the waveform of ECDM and surface craters, it is confirmed that the spark action is in the form of an arc. Compared to EDM, the volume of an arc eroded crater of ECDM was less than that of EDM. An XRD analysis of the phases of the EDM and ECDM specimens showed that the Al_4C_3 phase was detected on the former but not on the latter.