Interdiffusion coefficients in the B2 FeAl phase at 46 to 50at%Al were measured at 1173 to 1473K, under pressures ranging from 0.1MPa to 5GPa (figure 4). The activation volume for interdiffusion, EV, as derived from the pressure dependence of the interdiffusion coefficient, was 0.58 to 0.90Vm (table 2); where Vm was the molar volume of the alloy. This was comparable to, or larger than, the 0.4 to 0.6Vm values for the monovacancy mechanism in body-centered cubic pure metals or random alloys. The value of EV increased with increasing temperature and also with deviations from stoichiometry. This suggested that divacancies contributed to diffusion at higher temperatures and in the off-stoichiometry region.

Interdiffusion in B2 Type Intermetallic Compound FeAl under High Pressures. R.Nakamura, Y.Yamazaki, Y.Iijima: Materials Transactions, 2003, 44[1], 78-82

Figure 4

Interdiffusion Coefficients in FeAl

(a: 1473K 0.1MPa, b: 1473K 3GPa, c: 1473K 4GPa, d: 1473K 5GPa,

e: 1173K 0.1MPa, f: 1173K 3GPa, g: 1173K 4GPa, h: 1173K 5GPa)