Microstructure characteristic, mechanical properties and sintering mechanism of nanocrystalline copper obtained by SPS process

Nano-sized copper powder with an average size of 50 nm fabricated by chemical reduction method of hydrazine hydrate was consolidated using spark plasma sintering (SPS) method. The relationship between the sintering temperature and relative density of the nanocrystalline bulk copper was studied, the microstructure and the mechanical properties were examined, and the sintering mechanism was discussed. It was concluded that the nanocrystalline copper with a relative density greater than 99% and the yield strength of nearly 650 MPa could be fabricated by SPS process with the holding pressure of 600 MPa, sintering temperature of 350 °C, holding time of 5 min, and heating rate of 100 °C/min. Both refinement of the grains and formation of the extensive nanoscale twins in the NC bulk copper are the main factors to strengthen the metal.