The segregation of P at between 783 and 923K was studied by using Auger techniques. The segregation kinetics were consistent with a model which assumed that the rate-controlling process was the bulk diffusion of P. It was concluded that P diffusion in Fe could be described by the expression:

D (cm2/s) = 8 x 105 exp[-314(kJ/mol)/RT]

Similar results were obtained in the case of C-free alloys. It was concluded that an increase in activation energy with decreasing temperature was consistent with previous observations of a decrease in diffusion activation energy below the ferromagnetic transition temperature.

G.Luckman, R.A.Didio, W.R.Graham: Metallurgical Transactions, 1981, 12A[2], 253-7

 

Table 25

Lattice Diffusion Parameters for 22P in Fe

 

P (at%)

Phase

Do (m2/s)

E (kJ/mol)

-

paramagnetic

2.87 x 10-2

271

-

ferromagnetic

1.38 x 101

332

0.16

paramagnetic

3.76 x 10-2

275

0.16

ferromagnetic

1.08 x 10-1

288

0.18

paramagnetic

2.55 x 10-3

247

0.18

ferromagnetic

1.06 x 103

359

0.38

paramagnetic

8.87 x 10-3

259

0.38

ferromagnetic

4.90 x 100

316