Diffusion couple has been set up for pure copper and aluminum. The diffusion coe

Question

Diffusion couple has been set up for pure copper and aluminum. The diffusion coefficients for copper in aluminum at 500 and 600%uF0B0C are 4 x 10-14 and 5.3 x 10-13 m2/sec, respectively. Determine the time at 500%uF0B0C that will produce the same diffusion results (in terms of concentration of Cu in Al) as a 10-hour heat treatment at 600%uF0B0C.

Hints:

(Ccu(x,t)-Ccu+00)/(Ccu-00-Ccu+00) = constant!

Also, the composition in both diffusion situations (i.e., 500%uF0B0 and 600%uF0B0C) will be equal at the

same position (i.e., x is also a constant).

Explanation / Answer

For same diffusion results ,diffusion coefficients x time = constant.

=>5.3 x 10-13 m2/sec x 10-hour = 4 x 10-14  m2/sec x time

=> time = 5.3 x 10-13 m2/sec x 10-hour / ( 4 x 10-14 m2/sec )

= 132.5 hours

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