Consider a diffusion couple composed of two semi-infinite solids of the same metal and that each side of the diffusion couple has a different concentration of the same elemental impurity; furthermore, assume each impurity level is constant throughout its side of the diffusion couple. For this situation, the solution to Ficks second law (assuming that the diffusion coefficient for the impurity is independent of concentration) is as follows: Cx = C2 + a C1 - C2 2 b c 1 - erfa x 21Dt b d (5.15) The schematic diffusion profile in Figure 5.13 shows these concentration parameters as well as concentration profiles at times t 0 and t 0. Please note that at t 0, the x 0 position is taken as the initial diffusion couple interface, whereas C1 is the impurity concentration for x 0, and C2 is the impurity content for x 0. Consider a diffusion couple composed of pure nickel and a 55 wt% Ni-45 wt% Cu alloy (similar to the couple shown in Figure 5.1). Determine the time this diffusion couple must be heated at 1000C (1273 K) in order to achieve a composiFigure 5.13 Schematic concentration profiles in the vicinity of the interface (located at x 0) between two semi-infinite metal alloys before (i.e., t 0) and after a heat treatment (i.e., t 0). The base metal for each alloy is the same; concentrations of some elemental impurity are differentC1 and C2 denote these concentration values at t 0. Position Concentration C1 t > 0 x < 0 x > 0 t = 0 x = 0 C2 C1 C2 2 164 Chapter 5 / Diffusion tion of 56.5 wt% Ni a distance of 15 m into the Ni-Cu alloy referenced to the original interface. Values for the preexponential and activation energy for this diffusion system are 2.3 104 m2 /s and 252,000 J/mol.

%ECE 102 assignment 6 problem solving %Mausam Rayamajhi PROBLEM STATEMENT To find whether the velocity of at the second point increases, decreases or remains the same as the first point INPUT AND OUTPUT Input = A1 and A2 output = V2 1. Enter the Area of the first point, A1 and area of the second point, A2 2. Initialize V1 = 3 3. Calculate V2 = (A1*V1)/A2; 4. If V2 > V1, print increased 5. Else if V2 = V1, print equal 6. else V2 < V1, print decreased 7. end Test If A1 = 1 and A2 = 3 then V2 would be 1 which will give an output, decreased If A1 = 9 and A2 = 3 then V2 would be 9 which will be an output, increased If A1 = 6 and A2 = 6 the V2 would be 3 which will be an output, equa