The Effects of Sintering Pressure Routes on the Microstructural Evolution and Mechanical Properties of Sintered Copper Via Sps

The Spark Plasma Sintering (SPS) is a pressure-assisted process in which high density and mechanical properties are usually reached. This study applied the SPS to consolidate copper powder using different sintering pressure routes during holding time or heating. In the first route, the pressure was maintained (around 15 MPa) during the heating up to the sintering temperature (650 ºC); the pressure was increased during the holding time. In the second route, the pressure was raised during the heating and kept constant during holding time at 650ºC. Three different pressure levels were applied on each route: 110, 65, and 50 MPa. Microstructural evolution was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In the first route, in which higher pressure rates were found, grain growth inhibition was observed, and densification was improved significantly. The increase in pressure also led to an increase in microhardness (17%), a decrease in pore volume fraction (10.5%), and an increase in pore circularity, causing substantial variations between the microstructures of samples. In addition, a finite element method (FEM) analysis was conducted using a thermo-mechanical approach to evaluate the stress distribution in the two different sintering routes. The results agree with the experimental results, and more pronounced effects were found in the first route because of higher compressive stresses.