The pressure and temperature dependences of 63Ni heterodiffusion was investigated at temperatures ranging from 888 to 1282K (table 10). This range included the critical temperature of the A2-B2 order-disorder transition. A radio-tracer method was used, combined with a serial sectioning technique. The high-pressure measurements showed that the diffusion process was controlled by mono-vacancies in both the ordered and disordered structures. The Arrhenius plot exhibited a downward curvature, as a result of B2-type ordering, and the lattice diffusion coefficients could be fitted by a continuous curve as a function of temperature and long-range order parameter. Because of the preference of Ni for α-sites, the Ni diffusivity was slower and the activation energy for diffusion was higher than the corresponding values for Fe self-diffusion.

Pressure and Temperature Dependence of Nickel Diffusion in Fe3Al: Effect of Ordering Z.Tôkei, J.Bernardini, G.Erdélyi, I.Gôdény, D.L.Beke: Acta Materialia, 1998, 46[13], 4821-5

 

 

 

Table 10

Diffusion of 63Ni in Fe3Al

 

Temperature (K)

Structure

P (kbar)

D (m2/s)

888

B2

1.0

9.84 x 10-19

933

B2

1.0

6.73 x 10-18

973.5

B2

0.1

8.4 x 10-17

973.5

B2

1.9

7.3 x 10-17

973.5

B2

3.3

5.8 x 10-17

973.5

B2

6.1

4.4 x 10-17

973.5

B2

8.6

3.3 x 10-17

1028

B2

1.0

2.60 x 10-16

1073

A2

0.1

1.2 x 10-15

1073

A2

0.6

1.7 x 10-15

1073

A2

1.0

8.80 x 10-16

1073

A2

1.0

1.08 x 10-15

1073

A2

1.9

1.8 x 10-15

1073

A2

4.0

8.9 x 10-16

1073

A2

6.3

9.2 x 10-16

1073

A2

8.5

8.0 x 10-16

1177

A2

1.0

1.17 x 10-14

1282

A2

1.0

6.84 x 10-14