The sintering rate during spark sintering of pure copper powder was measured and analyzed to investigate the sintering mechanism. After the initial stage of spark sintering, where the relative density is smaller than about 0.75 approx 0.8, relative density is decided only by their temperatures and the sintering rate is decided only by the heating rate at a constant pressure. The mechanism of sintering in this stage is plastic deformation according to this fact and it was suggested that local higher temperature regions by Joule heat generation are present close to the contacts of powder particles. In the next stage, where the relative density is larger than about 0.8 and the heating rate becomes very small, the sintering rate can he represented by the equation including power law creep mechanism.
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