A diffusion couple is made by joining pure Cu to Cu-10% Al, with inert markers in the weld interface. Annealing gives marker motion indicating DAl> DCu.

(a)Draw a plot of the concentration of Al vs. distance for the annealed couple. Be sure to indicate the difference in penetration distance on the two sides of the marker interface resulting from DAl> DCu.

(b)Show which way the markers at the interface will shift, and where the Kirkendall porosity will be growing most rapidly for the C(x)curve drawn in (a).