Interdiffusion experiments were carried out in Ta-W alloys using pure Ta and pure W as end-compositions in a diffusion couple. The
couple was annealed at 2100°C for 16 hours. At the end of the anneal, the diffusion couple was removed from the furnace and quenched. The
couple was then sectioned to expose the interior, and then analyzed to determine the concentration at that position. This was done using
electron microprobe analysis, yielding the concentration (atomic %) versus distance (microns) data graphed below.
Apply the Boltzmann-Matano method to these data and calculate the diffusivity, D(C’), as a function of concentration for the alloys formed in
the couple. Answer the following:
a) What is the location of the Matano interface (microns from Ta end of sample)?
b) Construct a plot of the diffusivity, D(C’), as a function of Tantalum concentration. Present the diffusivity in units of cm2/s.
c) At a composition of 40% Tantalum (Ta), what is the calculated diffusivity? Do you ‘‘trust’’ this value? Briefly explain.
d) How about at a composition of 90% Tungsten (W)?