DEFECT STRUCTURES IN METALS EXPOSED TO IRRADIATION OF DIFFERENT NATURE

The regularities of the defect structure formation in near-surface lay ers of metals and alloys under irradiation of different types are pres ented. Three types of irradiation were used to treat the targets: high -dose ion implantation (HDII), high-power ion beam (HPIB) and high-pow er pulsed microwave (HPPM). In the case of HDII the continuous and rep etitively-pulsed regimes were used. Different ions (B, C, Ar, Fe, Ni, Hf, Cu, Mo, Pb, Zr, La, W, Dy) of 40-200 keV energy were implanted to the irradiation dose of 1 x 10(16) to 1 x 10(18) ion cm(-2) in alpha-F e, Cu and Mo metals and Ni3Fe, Cu-Co-Al and VT18U alloys. Two-componen t pulsed HPIB (50% C + 50% H) was used to treat alpha-Fe. The energy o f ions was 300 and 400 keV, the ion current density was 60, 100 and 20 0 A cm(-2) and the pulse duration was about 100 ns. Cu, alpha-Fe, Ni a nd Mo metals were exposed to HPPM with wavelengths of 2.85 and 10.0 cm . The microwave power flux density was varied from 2 to 400 kW cm(-2), whereas the pulse duration was varied from 50 to 300 ns. The exposure to HDII, HPIB or HPPM irradiation leads to the generation of dislocat ions in the near-surface layer of metallic materials. The thickness of the near-surface layer with induced dislocation structure depends on the type of irradiation and is equal to several micrometres for HPPM, tens of micrometres for HDII and hundreds of micrometres for HPIB. The defect structures induced by irradiations mentioned above are similar to the defect structures formed in metals and alloys during plastic d eformation at one-axis tension or compression. The main reason for def ect structure formation in the metals exposed to irradiation is the hi gh level of stresses originating in the target near-surface layer. The mechanisms of stress origination, the value and the nature of the str esses are determined by the type of irradiation. (C) 1997 Elsevier Sci ence S.A.