Measurements were made of the tracer diffusivity in amorphous samples which had been prepared by melt-spinning in a vacuum. The diffusivity in as-quenched material was enhanced by the presence of quasi-vacancies. That is, excess free volume. During annealing, the quasi-vacancies were removed and the diffusivity tended to a constant value which depended only upon the temperature. The tracer self-diffusion of 57Co, at 513 to 693K, in relaxed amorphous material (table 77) could be described by:

D(m2/s) = 8.03 x 10-7 exp[-147(kJ/mol)/RT]

Appreciable atomic motion took place at temperatures where solid-state amorphization reactions occurred. This suggested that diffusion-limited growth of an amorphous phase could take place without nucleation of the more stable intermetallic compounds. The activation enthalpy for crystallization (335kJ/mol) was much higher than that for Co diffusion.

W.Dorner, H.Mehrer: Physical Review B, 1991, 44[1], 101-14

Figure 13

Diffusivity of Co in CoxZr1-x

 

Table 76

Diffusion of 195Au in Annealed Amorphous Co89Zr11

Temperature (K)

D (m2/s)

684

9.69 x 10-22

674

4.23 x 10-22

664

2.04 x 10-22

653

9.08 x 10-23

643

4.50 x 10-23

633

1.84 x 10-23

Table 77

Diffusion of 57Co in Annealed Amorphous Co89Zr11

 

Temperature (K)

D (m2/s)

693

7.16 x 10-18

682

4.53 x 10-18

673

3.46 x 10-18

654

1.46 x 10-18

633

6.58 x 10-19

613

3.30 x 10-19

602

1.75 x 10-19

583

5.68 x 10-20

574

2.86 x 10-20

552

6.99 x 10-21

533

3.03 x 10-21

513

1.49 x 10-21