Abstract
Specimens of Zircaloy-2 tubing material were irradiated with 1-MeV protons at temperatures of 200 and 350°C to doses of 0.01, 0.1, and 1.0 dpa, respectively. The original microstructure of the material before irradiation consisted of relatively coarse-grain (about 2.2 μm in diameter), low-dislocation-density, and randomly distributed intermetallic precipitates, namely Zr(Fe,Cr) 2 hexagonal close-packed (hcp), Zr(Fe,Cr) 2 face-centered cubic (fcc), and Zr 2 (Fe,Ni) body-centered tetragonal (bct). After proton irradiation at 350°C, it was observed that the precipitate morphology gradually coarsened with increasing dose and remained random in distribution. It was also found that the iron-to-chromium ratio was decreased in the Zr(Cr,Fe) 2 precipitates with increasing dose, especially around the edge of the precipitates. In the Zr 2 (Ni,Fe) precipitates, however, the iron-to-nickel ratio increased with increasing dose. A certain degree of recovery of the dislocation density was also observed in the irradiated specimens. Specimens irradiated at 200°C showed a rather different behavior. The precipitate morphology became a chain-like distribution with the particles located mostly along the grain boundaries in specimens irradiated to higher doses. Nodular corrosion test results indicated that the higher the irradiation dose the better the nodular corrosion resistance of this alloy. It is therefore concluded that irradiation-induced precipitate dissolution increases the solute concentration in the matrix and makes it more evenly distributed, which may in turn increase the nodular corrosion resistance of this alloy.