Session 2B Lectures by Fellows/Associates

Solving the issues of multicomponent diffusion

The diffusion community faced an unsolved challenge for several decades after the relations for the estimation of the diffusion coefficients in inhomogeneous multicomponent material systems were established based on the Onsager formalism. These could not be estimated experimentally in a system with more than three components fulfilling the mathematical complications and associated stringent experimental requirements. This led to an unbridgeable gap between the fundamental studies conducted in simpler systems and the need for understanding the diffusion phenomenon in various multicomponent systems in applications. We have now solved these issues by developing the concept of pseudo-binary and pseudo-ternary diffusion couple methods. These reduce the complications significantly for estimation of both main and cross interdiffusion coefficients. These are further extended for the estimation of the tracer and intrinsic diffusion coefficients from multicomponent diffusion profiles by developing new equations, which were considered impossible until now. The usefulness of these methods is demonstrated by explaining the diffusion-controlled microstructural evolution between single crystal superalloy and bond coat in jet engine.