Observation of Particle Behaviors in the Copper Powder Compact during Pulsed Electric Discharge

Behaviors of monosized spherical copper powder particles of 550 mm average diameter in the powder compact was observed under optical microscope during singlepulsed electric discharge for 500 ms. The morphologies of necks between powder particles were observed under scanning electron microscope and diameters of necks were measured. The results obtained were summarized as follows: It was confirmed that if the spark occurs or not depends on the pressure and pulsed current density. The spark at the interparticle contacts occurred more frequently, as the pressure was smaller and the current density was larger. Each particle was joined together by melting where the spark occurred. However, regardless the spark was observed or not, the necks were formed at the interparticle contacts and diameters of necks increased with increasing pulsed current density. It was suggested that microscopic spark, melting and vaporization occur due to extremely high temperature by the local heat generation at the interparticle contacts in the initial stage of compaction.