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The warping deformation along grain boundaries has been found for thin plates of Cu-1.8 mass%Be-0.2 mass%Co and Cu-1.8 mass%Be-0.2 mass%Co-0.03 mass%Mg alloys aged at 593 K for 3 h after cold rolling to 0% and 20% reduction, but not been detected for the two alloys aged at the same condition after cold rolling to 90% reduction, by surface roughness measurements. The aging produces 0 precipitates in grains and discontinuous precipitation (DP) cells at grain boundaries in the two alloys after 0% and 20% cold-rolling, but no DP cells in the alloys after 90% cold-rolling. The addition of Mg or the increase in cold-rolling rate decreases the width of DP cells, resulting in reduction in the degree of warping deformation. The warping deformation along grain boundaries can be attributed to the difference between the length changes of the DP cell and the grain interior by the aging.

The enhancement in tensile properties of a Cu2.0 mass%Ni0.5 mass%Si0.1 mass%Zr alloy without reducing its electrical conductivity is attempted by combining both accumulative roll-bonding (ARB) and cryo-rolling with aging treatment. The grain sizes of the alloy pre-aged at 450°C and ARB-processed in six cycles (P-ARB) and of the alloy pre-aged at 450°C and cryo-rolled to a 90% reduction (P-90CR) are refined to about 0.1 and 0.2 µm, respectively. Both six cycles of ARB and 90% cryo-rolling, together with the presence of fine precipitates formed by preaging at 450°C, give significant grain refinement. The P-90CR alloy aged at 350°C exhibits a higher 0.2% proof stress of 830 MPa and a higher tensile strength of · u = 900 MPa than the P-ARB alloy aged at 375°C. The aged P-90CR alloy exhibits almost the same elongation of 6% up to failure and the same electrical conductivity of · = 45% IACS as the aged P-ARB alloy. The higher proof stress of the aged P-90CR alloy than the aged P-ARB alloy is ascribed to the higher dislocation density in the aged P-90CR alloy. The value of · u = 900 MPa for the aged P-90CR alloy is larger than that of · u μ 830 MPa for conventional commercial Cu3.0 mass%Ni0.65 mass%Si system alloys. The value of · for the former alloy is nearly identical to · μ 46% IACS for the latter alloys.

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The microstructures of four kinds of Zircaloy-2-type materials with neutron exposure up to about 15 × 1025 n/m2 (E>1MeV) were examined to investigate the microstructural evolution and to correlate it with the in-reactor corrosion behavior at very high fluences. The materials examined in this study included two advanced Zr-based alloys with good corrosion resistance, namely High Fe Zry and High FeNi Zry, and two other kinds of Zry-2 materials with slightly different elemental compositions and fabrication processes producing differing second phase particle sizes. All alloys showed good corrosion behavior and low hydrogen pickup when irradiated up to four cycles in dummy neutron source holders located outside of channel boxes. After six irradiation cycles, all four of the alloys had an increase in the rate of uniform corrosion and hydrogen pickup. The results of the microstructure examinations after six-cycle irradiation indicated two interesting points: (1) increased insight into the dissolution process for Zr-Fe-Cr particles, and (2) a correlation between the number density of Zr-Fe-Cr particles surviving through irradiation and the corrosion behavior at high fluences. From these results, it is suggested that increasing the initial particle size and/or controlling the alloy chemistry would be beneficial to improve the uniform corrosion performance and to lower hydrogen pickup, especially at very high fluences.