The self-diffusion of Fe, and the impurity diffusion of In and Zn, was investigated by using the radiotracer technique and the isotopes 59Fe, 114mIn and 65Zn. The Zn and In were chosen with the aim of simulating Al diffusion; for which no feasible radio-isotope was available. It was found that the diffusivities of In and Zn were slightly higher than that of Fe, in all cases. Most of the measurements were performed in the B2-structure regions of the phase diagram, plus some in the A2-structure region and a few in the D03-structure region. There were 2 ordering transitions in Fe3Al; between A2 and B2, and between B2 and D03. Both of them led to an increase in the activation enthalpy for diffusion in the phase having the higher degree of order. With increasing Al content, the activation enthalpy for diffusion increased, even though the melting point decreased significantly. The data (tables 9 to 17, figures 7 to 15) could be described by:

59Fe in Fe74.5Al25.5 (A2):     D (m2/s) = 8.1 x 10-5 exp[-2.26(eV)/kT]

59Fe in Fe74.5Al25.5 (B2):     D (m2/s) = 3.8 x 10-4 exp[-2.40(eV)/kT]

59Fe in Fe74.5Al25.5 (D03):     D (m2/s) = 3.3 x 10-3 exp[-2.88(eV)/kT]

114mIn in Fe74.5Al25.5 (A2/B2):     D (m2/s) = 1.9 x 10-4 exp[-2.22(eV)/kT]

65Zn in Fe74.5Al25.5 (A2/B2):     D (m2/s) = 1.8 x 10-4 exp[-2.29(eV)/kT]

59Fe in Fe67Al33 (A2/B2):     D (m2/s) = 1.1 x 10-3 exp[-2.50(eV)/kT]

114mIn inFe67Al33 (A2/B2):     D (m2/s) = 2.1 x 10-3 exp[-2.48(eV)/kT]

65Zn in Fe67Al33 (A2/B2):     D (m2/s) = 4.3 x 10-3 exp[-2.49(eV)/kT]

59Fe in Fe52Al48 (B2):     D (m2/s) = 4.1 x 10-3 exp[-2.72(eV)/kT]

114mIn in Fe52Al48 (B2):     D (m2/s) = 5.4 x 10-3 exp[-2.66(eV)/kT]

65Zn in Fe52Al48 (B2):     D (m2/s) = 1.2 x 10-2 exp[-2.60(eV)/kT]

The results were explained in terms of information, on the defect structures, which were available from Mössbauer, positron annihilation, differential dilatometry, mechanical spectroscopic and resistivity data as well as on the basis of theoretical results arising from ab initio calculations of defect properties.

Diffusion in Intermetallic Phases of the Fe-Al System. M.Eggersmann, H.Mehrer: Philosophical Magazine A, 2000, 80[5], 1219-44

Figure 7

Diffusivity of 59Fe in Fe74.5Al25.5

 

Figure 8

Diffusivity of 59Fe in Fe67Al33

 

Figure 9

Diffusivity of 59Fe in Fe52Al48

 

Figure 10

Diffusivity of 114mIn in Fe74.5Al25.5

 

Table 9

Diffusivity of 59Fe in Fe3Al

 

Temperature (K)

Method

D (m2/s)

Structure

1475

dripping

1.49 x 10-12

A2

1377

dripping

4.83 x 10-13

A2

1275

dripping

1.37 x 10-13

A2

1226

dripping

4.03 x 10-14

A2

1168

dripping

1.81 x 10-14

A2

1124

dripping

5.88 x 10-15

A2

1067

dripping

1.64 x 10-15

B2

1030

dripping

6.69 x 10-16

B2

975

dripping

1.43 x 10-16

B2

920

dripping

2.82 x 10-17

B2

877

implantation

5.66 x 10-18

B2

816

implantation

4.75 x 10-19

D03

772

implantation

4.99 x 10-20

D03

724

implantation

2.59 x 10-21

D03

 

Figure 11

Diffusivity of 114mIn in Fe67Al33

 

Table 10

Diffusivity of 59Fe in Fe2Al

 

Temperature (K)

Method

D (m2/s)

Structure

1470

dripping

4.13 x 10-12

A2

1378

dripping

8.36 x 10-13

A2

1278

dripping

1.23 x 10-13

B2

1176

dripping

1.89 x 10-14

B2

1082

dripping

2.03 x 10-15

B2

977

implantation

1.20 x 10-16

B2

875

implantation

5.70 x 10-18

B2

776

implantation

6.64 x 10-20

B2

 

Figure 12

Diffusivity of 114mIn in Fe52Al48

 

Table 11

Diffusivity of 59Fe in FeAl (B2 Structure)

 

Temperature (K)

Method

D (m2/s)

1471

dripping

2.75 x 10-12

1372

dripping

4.16 x 10-13

1272

dripping

6.10 x 10-14

1175

dripping

7.63 x 10-15

1076

implantation

9.29 x 10-16

982

implantation

5.00 x 10-17

877

implantation

8.69 x 10-19

775

implantation

9.77 x 10-21

 

Figure 13

Diffusivity of 65Zn in Fe74.5Al25.5

 

Table 12

Diffusivity of 114mIn in Fe3Al

 

Temperature (K)

Method

D (m2/s)

Structure

1370

dripping

1.84 x 10-12

A2

1273

dripping

4.78 x 10-13

A2

1175

dripping

8.48 x 10-14

A2

1081

dripping

1.20 x 10-14

B2

973

dripping

8.58 x 10-16

B2

872

dripping

4.13 x 10-17

B2

780

implantation

6.2 x 10-19

D03

722

implantation

3.9 x 10-20

D03

 

Figure 14

Diffusivity of 65Zn in Fe67Al33

 

Figure 15

Diffusivity of 65Zn in Fe52Al48

 

Table 13

Diffusivity of 114mIn in Fe2Al

 

Temperature (T)

Method

D (m2/s)

Structure

1374

dripping

2.08 x 10-12

A2

1275

dripping

4.05 x 10-13

B2

1174

dripping

3.93 x 10-14

B2

1075

dripping

4.29 x 10-15

B2

972

dripping

3.58 x 10-16

B2

880

evaporation

1.68 x 10-17

B2

776

evaporation

1.76 x 10-19

B2

 

Table 14

Diffusivity of 114mIn in FeAl (B2 Structure)

 

Temperature (T)

Method

D (m2/s)

1374

dripping

1.10 x 10-12

1274

dripping

1.47 x 10-13

1174

dripping

1.99 x 10-14

1067

dripping

1.34 x 10-15

977

implantation

1.08 x 10-16

876

implantation

2.79 x 10-18

 

 

Table 15

Diffusivity of 65Zn in Fe3Al

 

Temperature (K)

Method

D (m2/s)

Structure

1370

dripping

1.42 x 10-12

A2

1271

dripping

3.42 x 10-13

A2

1228

dripping

1.34 x 10-13

A2

1176

dripping

9.31 x 10-14

A2

1172

dripping

8.15 x 10-14

A2

1128

dripping

2.44 x 10-14

A2

1079

dripping

1.03 x 10-14

B2

971

dripping

6.03 x 10-16

B2

869

dripping

3.39 x 10-17

B2

773

evaporation

3.76 x 10-19

D03

733

evaporation

2.54 x 10-19

D03