The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10-11 m-2 s-1. Assume the diffusion couple to be infinitely long. <img src="/images/question-image/metallurgical-engineering/physical-metallurgy/1684342519-M2-B-7-82.PNG" title="Physical Metallurgy mcq question image" alt="Physical Metallurgy mcq question image"> Which of the parameters give the composition profile in the following form? $$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

A

0.05

B

0.10

C

0.50

D

0.85

A

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}\exp \left$$

B

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}erf\left$$

C

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}\left$$

D

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}t$$

A

100

B

130

C

160

D

190

A

Column 1