ABSTRACT
The results of a tungsten-niobium alloy synthesis by the impact of pulsed compression plasma flows are presented. Tungsten plates with a 2 µm thin niobium coating were treated with dense compression plasma flows generated by a quasi-stationary plasma accelerator. The plasma flow with an absorbed energy density of 35-70 J/cm2 and pulse duration of 100 µs melted the niobium coating and a part of the tungsten substrate, which caused liquid-phase mixing and WNb alloy synthesis. Simulation of the temperature distribution in the top layer of the tungsten after the plasma treatment proved the formation of the melted state. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the structure and phase composition. The thickness of the WNb alloy was 10-20 µm and a W(Nb) bcc solid solution was found.
ABSTRACT
High-entropy alloys (HEAs) have prospects for use as nuclear structural materials. Helium irradiation can form bubbles deteriorating the structure of structural materials. The structure and composition of NiCoFeCr and NiCoFeCrMn HEAs formed by arc melting and irradiated with low-energy 40 keV He2+ ions and a fluence of 2 × 1017 cm-2 have been studied. Helium irradiation of two HEAs does not change the elemental and phase composition, and does not erode the surface. Irradiation of NiCoFeCr and NiCoFeCrMn with a fluence of 5 × 1016 cm-2 forms compressive stresses (-90 -160 MPa) and the stresses grow over -650 MPa as fluence increases to 2 × 1017 cm-2. Compressive microstresses grow up to 2.7 GPa at a fluence of 5 × 1016 cm-2, and up to 6.8 GPa at 2 × 1017 cm-2. The dislocation density rises by a factor of 5-12 for a fluence of 5 × 1016 cm-2, and by 30-60 for a fluence of 2 × 1017 cm-2. Stresses and dislocation density in the HEAs change the most in the region of the maximal damage dose. NiCoFeCrMn has higher macro- and microstresses, dislocation density, and a larger increase in their values, with an increasing helium ion fluence compared to NiCoFeCr. NiCoFeCrMn a showed higher radiation resistance compared to NiCoFeCr.
ABSTRACT
The purpose of this study is to assess the effect of doping ZrO2 ceramics with MgO on radiation swelling and polymorphic transformations, as a result of irradiation with heavy ions. Interest in these types of materials is due to the great prospects for their use as structural materials for new-generation reactors. The study established the dependences of the phase composition formation and changes in the structural parameters following a change in the concentration of MgO. It has been established that the main mechanism for changing the structural properties of ceramics is the displacement of the cubic c-ZrO2 phase by the Zr0.9Mg0.1O2 substitution phase, which leads to an increase in the stability of ceramic properties to irradiation. It has been determined that an increase in MgO concentration leads to the formation of an impurity phase Zr0.9Mg0.1O2 due to the type of substitution, resulting in changes to the structural parameters of ceramics. During studies of changes in the strength properties of irradiated ceramics, it was found that the formation of a phase in the Zr0.9Mg0.1O2 structure leads to an increase in the resistance to cracking and embrittlement of the surface layers of ceramics.
