Strengthening and Void Formation in the Mo-Zr-B Alloy Under Neutron Irradiation

The effect of neutron irradiation on the mechanical properties, structure, and peculiarities of void formation in the Mo-Zr-B alloy within the temperature range from 400 to 1080° C and fluences (1.3 to 11.5) · 10²⁵ n/m² (>0.1 MeV) has been investigated. The results from radiation studies of poly- and monocrystalline molybdenum, Mo—0.12 Zr—0.16 Ti alloy and of the Mo-Zr-B alloys with different initial thermal treatment have been analyzed. At temperatures of 950 and 1080°C, the voids of nonequiaxial shape are formed, and at 1010°C only planar defects, supposedly thin precipitates, are observed. These results show a minimum swelling of the Mo-Zr-B alloy at 1010°C. It is expected that the peculiarities of void evolution in the Mo-Zr-B alloy are due to the impurity precipitation on void faces. A good correlation of the calculated and experimental values for radiation strengthening of the alloy as a result of voids and dislocation loops within a wide range of their sizes and concentrations was observed. A connection was found between the reduction of the uniform elongation within the temperature range from 400 to 900° C and voidage parameters. A maximum strengthening of the alloy takes place after irradiation at 635°C, which results from a high density of both 1.5-nm-diam voids and the dislocation loops.