Radiation Damage - Environmental Degradation of Metals - page 484

2. In the approximate temperature range of 0.35-0.6 T m , voids and a dislocation

structure are produced.

3. Above about 0.6 T m , displacement damage continuously anneals, and helium

may precipitate to form equilibrium bubbles.

The increase in yield stress has been well accounted for in terms of strengthen-
ing from the three main components of the irradiation-produced microstructure,
i.e., dislocation loops, network dislocation, and voids. In type 304 stainless steel,
samples irradiated at about 450

C have been shown [1] to contain a high concen-
tration of faulted interstitial loops and voids, with the deformation confined to
narrow channels within the matrix, whereas at 600

°

C the structure consists of a
dislocation network and voids, both present in relatively low concentrations, and
the deformation is nearly homogeneous, as observed in unirradiated stainless
steels. The dislocation structures as encountered are shown in Fig. 9.12.
Irradiation embrittlement arises as a result of one or a combination of any of
the following phenomena [1]:

°

1. Changes in flow properties due the interaction of dislocations with irradia-

tion-produced defects

2. Precipitation of transmutation-produced gases such as helium at potential

fracture sites such as grain boundaries, and possibly

3. Irradiation-induced segregation due to vacancy fluxes to sinks such as grain

boundaries, which are also potential fracture sites

REFERENCES

1. E. E. Bloom, Irradiation strengthening and embrittlement, in Radiation Damage in

Metals , N. L. Peteson and S. D. Harkness (eds.), American Society for Metals, 1976,
p. 295.

2. A. Seeger, Proc. Symp. Rediat. Damage Solids React. Mat ., Vlenna, IAFA, 1962,

p. 101.

3. J. R. Beeler, Phys. Rev ., Vol. 150, p. 470, 1966.

4. L. A. Beavan, R. M. Scanlan, and D. N. Seidman, Acta Met ., Vol. 19, p. 1339, 1971.

5. S. H. Paine and J. H. Kittel, Proceedings of the International Conference on the

Peaceful Uses of Atomic Energy , Vol. 7, United Nations, 1956, p. 445.

6. L. L. Seigle and A. J. Opinsky, U. S. Atomic Energy Comm., Report SEP-160 (1954)

quoted in Radiation Effects in Solids , G. J. Dienes and G. H. Vineyard (eds.), Inter-
science, New York, 1957, p. 187.

7. R. J. McElroy, J. Nucl. Mat ., Vol. 90, p. 297, 1980.

8. D. O. Northwood, Atom. Energy Rev ., Vol. 15, p. 547, 1977.

9. S. F. Pugh, Ref. 5, p. 441.

10. G. J. Dienes and G. H. Vineyard, Radiation Effects in Solids , Interscience, New

York, 1957, p. 183.

11. S. R. MacEwen and G. J. C. Carpenter, J. Nucl. Mat ., Vol. 90, p. 108, 1980.