Isothermal relaxation of the short-range order was investigated by making residual electrical resistivity measurements at 4.2K. Short range ordering resulted in an increase in electrical resistivity, and the equilibrium values of this property (which characterized the short-range order equilibrium states) varied linearly as a function of the reciprocal temperature. An analysis of the results by using phenomenological laws permitted the determination of characteristic time constants and the activation enthalpies for self-diffusion. It was found that the parameters which were deduced by using different types of analysis were usually in good agreement (table 171). A comparison with results for binary solid solutions showed that the presence of Ta or Ti (with 4at%Al) significantly reduced atomic mobility in these alloys.

T.Tarfa, B.Sitaud, O.Dimitrov: Acta Metallurgica et Materialia, 1993, 41[11], 3191-202

Table 171

Diffusion Parameters for Self-Diffusion in Ni-Al-Ta Alloys,

as Deduced using Various Techniques and Analyses

 

Al(at%)

Ta(at%)

Technique

Analysis

o(s)

E(eV)

4

2

both

power law

6.2 x 10-18

2.96

4

2

down-quenching

power law

1.4 x 10-18

3.05

4

2

both

distribution law

3.7 x 10-18

3.00

4

2

down-quenching

distribution law

1.8 x 10-19

3.18

4

0

both

power law

8.8 x 10-15

2.79

4

0

down-quenching

power law

6.6 x 10-20

3.22

4

0

up-quenching

power law

8.5 x 10-15

2.54

4

0

both

distribution law

1.3 x 10-17

2.92

4

0

down-quenching

distribution law

3.0 x 10-21

3.41

4

0

up-quenching

distribution law

1.6 x 10-17

2.95

3

0

both

power law

3.3 x 10-16

2.67

3

0

both

distribution law

1.1 x 10-17

2.61