Evaluating Interdiffusion Matrices in High Temperature Ternary Alloys
Extracting ternary interdiffusion matrices requires intersecting diffusion paths, rigorous molar volume corrections, and thermodynamic constraints.
Kirkaldy Intersection
Meaning
Geometric location on a concentration profile marks the point where the flux of a component vanishes despite the presence of a gradient. The kirkaldy intersection occurs because of the interaction between different chemical species as they migrate through the lattice. It demonstrates that the movement of one atom is coupled to the gradients of all other components in the alloy.
Theoretical Origin
Phenomenological equations describe how chemical potentials drive atomic transport in complex mixtures. J.S. Kirkaldy proposed this concept to explain zero flux planes observed in experimental diffusion couples. The kirkaldy intersection reveals the complexity of uphill diffusion where species move against their own concentration gradient.
Flux Measurement
Determination of the intersection point requires precise mapping of concentration profiles using electron probe microanalysis. Analyzing the slope at the specific location where the integrated area under the curve is zero identifies the phenomenon. The kirkaldy intersection provides a test for the accuracy of multicomponent diffusion models.
Experimental Application
Research into nickel based superalloys often utilizes these points to calculate cross term diffusion coefficients. Understanding where flux stops is necessary for predicting the stability of protective coatings at high temperatures. The kirkaldy intersection defines the limit of independent atomic movement.