The diffusion of Al-replacing elements was investigated (tables 12 and 13), over a wide temperature range, in single crystals with the composition: Ni75.9Al24.1. The concentration profiles were measured by means of secondary ion mass spectrometry. A model was suggested for minority-component diffusion, via anti-structure defects, in the L12 structure. It involved nearest-neighbor jumps of solute atoms on the Ni sub-lattice, as anti-structure atoms, and the formation of so-called anti-structure bridges which corresponded to jumps between different sub-lattices. The model was shown to agree with experimental data on Al-replacing solute diffusion, and it explained the observed ratio of the self- to solute-diffusivities. This ratio could be higher or lower than unity; depending upon the solute and upon the temperature.

Solute Diffusion of Al-Substituting Elements in Ni3Al and the Diffusion Mechanism of the Minority Component S.V.Divinski, S.Frank, U.Södervall, C.Herzig: Acta Materialia, 1998, 46[12], 4369-80

 

 

 

Table 12

Bulk Diffusion of Al-Replacing Solutes in Ni3Al Single Crystals

 

Diffusant

Temperature (K)

D (m2/s)

Ga

1005

9.93 x 10-21

Ga

1053

5.95 x 10-20

Ga

1080

3.51 x 10-19

Ga

1176

5.31 x 10-18

Ga

1278

9.52 x 10-17

Ga

1320

3.89 x 10-16

Ga

1370

1.04 x 10-15

Ga

1422

3.90 x 10-15

Ge

1047

4.30 x 10-20

Ge

1090

2.11 x 10-19

Ge

1154

2.53 x 10-18

Ge

1226

2.05 x 10-17

Ge

1306

2.45 x 10-16

Ge

1355

5.30 x 10-16

Ti

1090

5.05 x 10-21

Ti

1158

5.48 x 10-20

Ti

1222

4.45 x 10-19

Ti

1256

1.65 x 10-18

Ti

1306

1.12 x 10-17

Ti

1385

7.55 x 10-17

Ti

1453

5.59 x 10-16

Nb

1157

8.81 x 10-21

Nb

1216

1.10 x 10-19

Nb

1254

3.10 x 10-19

Nb

1300

2.18 x 10-18

Nb

1327

5.31 x 10-18

Nb

1372

1.73 x 10-17

Nb

1408

5.48 x 10-17

Nb

1444

1.84 x 10-16

 

 

 

Table 13

Arrhenius Parameters for Bulk Diffusion in Ni3Al

 

Diffusant

Do (m2/s)

Q (kJ/mol)

Ga

0.0787

363.1

Ge

0.107

368.6

Ti

0.859

424.6

Nb

25.8

475.6