Investigation of MoSi2 formation in the presence of copper by self-propagating high-temperature synthesis

Combustion reactions in the Cu-Mo-Si system were investigated. A sample was ignited using electric arc and after completion of the combustion reaction, XRD, SEM and EDS analysis were carried out. The resulting microstructure consisted of almost spherical grains of MoSi2. Also a little amount of Mo-rich silicides (Mo5Si3, Mo3Si) and copper silicides were present at the grain boundaries. For investigating the formation mechanism of this microstructure, another sample was ignited and when the combustion wave was almost in the middle of the sample, the compact was quenched into liquid nitrogen. The results indicated that at the leading edge of combustion front, liquid solution of Cu-Si forms. The Mo particles dissolve in this melt and after that MoSi2 precipitates. By growing MoSi2 particles, remaining melt becomes richer in Cu which finally solidifies in cooling.