Silver and Gold form a continuous series of solid solutions, and interdiffusion occurs by a vacancy mechanism. A diffusion couple was made by depositing a thick layer of Silver onto a gold substrate. At $1000$ K the interdiffusion coefficient of silver into gold is $10-10$ cm$2/$s and the interdiffusion coefficient of gold into silver is $2$ x $10-11$ cm$2/$s$.$

a$)$ Whycanthetwodiffusioncoefficientsbedifferent?

b$)$ Will the plane where the concentration if $50$:$50($metallurgical interface$)$ move

during diffusion? If so$,$ which way.

c$)$ Will there be a net flux of vacancies through the inter during diffusion?On

which side of the interface would you expect to find voids $($pores$)?$

d$)$ Sketch the concentration profile at the junction after annealing at for $3$ days at

$1000$K