Effect of Neutron Irradiation on Copper Crystals at High Temperatures

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Abstract
Etching, x‐ray topography, and electron‐microscopy studies have shown that neutron irradiation at about 400°C produces a defect structure different from that produced by irradiation at ambient temperatures. On a macroscopic scale the damage was nonhomogeneous; there were regions containing high concentrations of defects separated by apparently perfect crystal. The size of the defect regions ranged from 10–100 μ, and the distance between regions was ∼100 μ. Borrmann topographs showed long‐range order among the defect regions in that they tended to be aligned in habit planes parallel to (111) planes. Measurements of the absolute integrated intensities of Borrmann diffracted beams indicated that there must have been a large degree of elastic strain between defect regions. It has been shown that the defect regions were aggregates of large dislocation loops 1000–2000 Å in diameter, dislocation tangles of roughly the same dimension, smaller loops 50–150 Å in diameter, and three‐dimensional point defect clusters 200 Å or less in dimension. The larger loops were principally interstitial, the smaller loops were principally vacancy type. The concentration of vacancies and interstitials within defect regions, as estimated from the loops and clusters, was 1.6×1018/cm3 and 2×1018/cm3, respectively, which averaged to about 3×1016/cm3 for the entire crystal. These high‐temperature irradiation effects were somewhat independent of the state of perfection of the specimens; defect regions were observed in polycrystal as well as single‐crystal specimens. Annealing of the high‐temperature damage occurred nonhomogeneously between 500° and 800°C, a higher range than that for annealing damage produced at ambient temperatures. Defect regions remote from as‐grown dislocations were annealed at the lower temperatures, while those near dislocations required anneals at 800°C.