Title

Error analysis and measurement of the square root diffusivity with applications to Ni-Cr-Al $\beta$-alloys at 1200$\sp\circ$C

Date of Completion

January 1997

Keywords

Engineering, Metallurgy|Engineering, Materials Science

Degree

Ph.D.

Abstract

Two analyses for determining the square root diffusivity were compared and contrasted. One analysis uses two diffusion couples to determine the four square root diffusion coefficients of a ternary alloy while the other analysis uses only one diffusion couple. The analyses were applied to a series of Ni-Cr-Al $\beta$-alloys at 1200$\sp\circ$C. It was found from the experimental data and a theoretical analysis that the method which uses two diffusion couples has significantly less error than the method that uses one diffusion couple. However, if one is interested in measuring only one column of the square root diffusivity matrix, then the two analyses have the same error. In addition it was shown that agreement between the error function solution to the diffusion equation and the concentration profiles of one diffusion couple could not be used to verify a square root diffusivity matrix. ^