Microstructural evolution and sintering kinetics during spark plasma sintering of Fe and Al blended powder

The reaction diffusion between Fe and Al during spark plasma sintering (SPS) was studied. Microstructural evolution was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the sintering kinetics was disclosed. The main interphase of the SPS sample was Fe2Al5 at 773-873 K. Ball-milling enabled a large number of lattice defects and grain boundaries thus the reaction kinetics was accelerated, although the direct current can also promote those defects. After milling, the phase transformation kinetics was improved from 0.207 before mill to 4.56×10−3. Besides, this work provided more details for the generation of Joule heating. The resistance offered to the electric path was considered to be the source of Joule heating, and particularly the resistance offered by the different contact interfaces of die, punch, graphite foil and the sample played a leading role for the generation of Joule heating during spark plasma sintering.