Interface evolution and shear strength of Al/Ti bi-metals processed by a spark plasma sintering (SPS) apparatus

Microstructural evolution of the Al/Ti bi-metal interface during heat treatment in a spark plasma sintering (SPS) apparatus was investigated under various conditions for the first time. A mechanism of interfacial layer growth was suggested based on the results of SEM, TEM and X-ray diffraction analysis. A continuous TiAl3 intermetallic layer was formed at the Al/Ti interface even after a processing time as short as about a minute. The TiAl3 layer grew mainly into the Ti part, while only a few individual grains grew into the Al part. Evolution of the interlayer was determined by Al diffusion through the (TiAl3/TiAl3) grain boundary. The activation energy of the process was 140 kJ/mol. The shear strength of the interface in the Al/Ti bi-metal was determined after various heat treatments. The shear strength of the bi-metal was limited by the properties of aluminum, with no effect of interlayer thickness or current mode and pulse pattern of the SPS treatment being detected.