Experiments were performed by using electrochemical methods, and steel membranes which were subjected to various stresses. In one series of tests, the stress was kept constant and 2 successive permeations were conducted (table 118). In a second series, an increasing stress was applied during the stationary stage of preliminary permeation. Anomalies of various types were encountered: these were a decreasing diffusion coefficient during the first permeation in the first series of experiments (table 119), and an abnormal decrease in the exit flux after dynamic loading in the second series. It was shown that they could be quantitatively interpreted in terms of an irreversible trapping which was induced by plastic deformation.

J.B.Leblond, D.Nejem, D.Dubois, S.Talbot-Besnard: Acta Metallurgica, 1987, 35[7], 1703-14

 

Table 118

Permeation of H in Deformed A508 Steel

 

Domain

Stress (MPa)

Strain (%)

Permeation

Permeability (ppm mm2/s)

elastic

0

-

first

6.3 x 10-5

elastic

0

-

second

8.5 x 10-5

elastic

200

-

first

5.5 x 10-5

elastic

200

-

second

7.3 x 10-5

elastic

400

-

first

6.8 x 10-5

elastic

400

-

second

8.9 x 10-5

plastic

-

1

first

6.9 x 10-5

plastic

-

1

second

1.1 x 10-4

plastic

-

2

first

5.6 x 10-5

plastic

-

2

second

9.8 x 10-5

Table 119

Diffusion of H in Deformed A508 Steel

 

Domain

Stress (MPa)

Strain (%)

Permeation

D (mm2/s)

elastic

0

-

first

2.32 x 10-4

elastic

0

-

second

2.23 x 10-4

elastic

200

-

first

1.71 x 10-4

elastic

200

-

second

1.96 x 10-4

elastic

400

-

first

1.70 x 10-4

elastic

400

-

second

1.74 x 10-4

plastic

-

1

first

1.55 x 10-4

plastic

-

1

second

1.78 x 10-4

plastic

-

2

first

1.14 x 10-4

plastic

-

2

second

1.43 x 10-4