Kinetics of combustion synthesis in Ti-C-3Ni-Al system

The Kinetics and mechanisms of the combustion reaction in the Ti-C-3Ni-Al system were studied. Samples were prepared by igniting compacts of eliminated Ti, C, Ni and Al powders with a heating tungsten coil under an inert argon atmosphere. The activation energies of Ti + C + 50wt% (3Ni + Al) -->TiC + 50% Ni3Al and Ti + C + 80wt% (3Ni + Al) --> TiC + 80%Ni3Al exothermic reactions were determined by measuring the combustion wave velocity and the combustion temperature, which are 129 kJ(.)mol(-1) and 79kJ(.)mol(-1), respectively. The mechanism of formation of products for Ti-C-3Ni-Al system was found: metal phases (Ti-3Ni-Al) are melted in combustion process, and carbon dissolves into the liquid metal and TiC is subsequently precipitated out of solution, and Ni3Al is crystallized during the cooling process. The mechanism is fairly similar with that of Ti + C --> TiC and Ti + C + Ni --> TiC + Ni. There are two reactions (Ti + C --> TiC, 3Ni + Al --> Ni3Al) in the Ti + C + 3Ni + Al system, and the wave velocity is mainly controlled by, the velocity of Ti + C --> TiC, but the velosity of 3Ni + Al --> Ni3Al may play a significant role when Ni3Al contents are higher than 70wt%.