Abstract
The results of studying the dependence of mechanical properties, corrosion and radiation resistances of hafnium rods on their structure are presented and reviewed in this paper. As observed, the rods in a fully recrystallized state with a fine-grained structure possess optimal mechanical properties (high strength and ductility). Tensile strength of these rods at room temperature is of $\approx$ 575 MPa, percentage elongation is of 27–28%. Autoclave corrosion tests and anode polarization curves reveal that oxide films formed on hafnium samples in a fully recrystallized state are the most protective that is due to the low surface activity at the medium–metal interface. The corrosion rate of such hafnium rods at the initial period of oxidation (before the pre-transition period) is well described by the empirical power equation with the power coefficient of 0.242 $\pm$ 0.015. After the transition point ($\approx$ 6000 h), the corrosion kinetics is described by a linear dependence with the oxidation rate of 3.12∙10$^{–4}$ $\pm$ 2.07∙10$^{–5}$ mg/(dm$^2$∙h). As shown, there is a correlation between the radiation growth of hafnium rods and their texture coefficient (Kearns’s parameter) according to the results of radiation tests carried out at the JSC ‘SSC RIAR’ (RF) as well as structural-textural studies of the same samples of hafnium rods in various structural states performed in this work. The results presented in this paper reveal that the coefficient of radiation growth linearly decreases with an increase of the Kearns’s parameter to a value of 0.33. This indicates that hafnium rod samples with a more isotropic texture are less susceptible to radiation growth. The radiation growths differ, depending on the rods’ structure. For rods with the same texture and different grain sizes, the samples with a fine-grained structure are less disposed to radiation growth. While Kearns’s parameters are similar, the hafnium rods with a coarse-grained structure show a higher rate of radiation growth. The deformation of the radiation growth of rods with a recrystallized structure, the Kearns’s parameter of $\approx$ 0.1, and an average grain size of less than 20 μm is almost equal to zero when the rods are irradiated at a temperature of 260–300°C up to a fast neutron fluence of 7.8∙10$^{21}$ cm$^{–2}$.