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 2100C 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)?