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Ti-AL-Mo ternary isotherm at 1200oc
The phenomenon of solid-state diffusion is of significant importance in Materials Engineering as it guides most of the processes including precipitation, dissolution, homogenization, welding, sintering and solid state alloying. Knowledge of fundamental diffusion behavior is of utmost importance in controlling and predicting the evolution of microstructure during these processes. Although unary and binary diffusion has widely been studied, diffusion behavior of multicomponent (ternary and higher order) systems still remains vastly unexplored. Interactions among diffusing species play crucial role in guiding the multicomponent diffusion processes; to the extent that they can even make a component diffuse against its own concentration gradients. Such multicomponent effects are not possible to predict with extrapolation of binary diffusion data to higher order systems in absence of ternary diffusion data. Hence, the objective of this study is to investigate interdiffusion in ternary alloys with specific emphasis on diffusional interactions and their relations with the basic thermodynamic factors.
Titanium alloys have widespread applications in various fields including aerospace, automobile and medical implants. However the use of Ti-alloys on mass-scale is still restricted due to the high costs associated with them. However, with the emergence of low-cost production techniques for pure Ti in powder form, solid-state alloying through the route of blended elemental powder metallurgy is gaining popularity. This makes the availability of multicomponent diffusion data in Ti-alloys even more desirable.
The ternary interdiffusion coefficients in Ti-Al-Mo system will be evaluated experimentally with diffusion couple experiments. The alloy compositions used for assembling diffusion couples will be selected based on the thermodynamic activity data so as to get prominent diffusional interactions within the couples. The multicomponent diffusion data will be used to model the homogenization kinetics in order to bring out the effects of the diffusional interactions in the Ti-Al-Mo alloys.