Question

Compute diffusion coefficients for the interdiffusion of carbon in both (a) α-iron (BCC) and (b) γ-iron (FCC) at 875˚C. Assume that D0 for the interdiffusion of carbon in α-iron and in γ-iron are 1.1 × 10-6 and 2.3 × 10-5 m2/s, respectively, and that Qd are 80 and 148 kJ/mol, respectively. (a) m2/s (b) m2/s

Calculate the value of D at 636°C for the diffusion of some species in a metal for which the values of D₀ and Q_d are 5.9 × 10^-5 m²/s and 167 kJ/mol, respectively.

The activation energy for the diffusion of atomic species A in metal B is 113 kJ/mol. Calculate the diffusion coefficient at 859°C, given that the value of D at 1190°C is 7.3 × 10^-11 m²/s.

Answer 1

Equation for diffusion constant, D is used here. D is obtained for alpha iron and gamma iron, for a species diffusing into metal and also for atomic species A in metal B. In the last case, D0 was not directly given but values was given. From that D0 was obtained and was put into the equation to get diffusion coefficient at required temperature.