Effect of Concentration of Mo on The Mechanical Behavior of UMo Fuel: An Atomistic Study

We performed molecular dynamics simulation on nanoindentation of Uranium Molybdenum alloys using spherical indenter. A ternary potential developed for UMoXe was utilized. We calculated the updated values for hardness and reduced elastic modulus at different concentrations of Mo. The whole process of deformation and dislocation analysis was visualized using OVITO. We found an increase in deformation with increase in stress while dislocations are not found anyhow induced defects have been distributed throughout the simulation cell randomly. The increase in concentration affected the hardness and reduced elastic modulus significantly.

Study of the Silicon Carbide Wear Area after Micro-Scratching of Titanium, Zirconium, Niobium and Molybdenum at a Speed of 35 m/s

The authors conducted the study at micro-scratching of titanium, zirconium, niobium and molybdenum alloys. The content of the main element in alloys was from 99.5 to 99.7 %. Micro-cutting was carried out by specially prepared indenters with silicon carbide mono-crystals of a given shape. The state of the relief and the chemical composition of the wear area were studied using a scanning two-beam electron microscope. The micro-scratching speed was 35 m/s without cooling. The condition of the contact surfaces of silicon carbide and metals was studied at a magnification up to 100,000 times with the rotation and tilt of the microscope slide. The content of chemical elements was determined at individual spots of an object by scanning along the line and area. The authors also studied the condition of the wear area after micro-scratching of metals and after removal of metal adhesions by chemical etching. The intensity of metal transfer was determined by the average concentration of metal atoms at the wear area. The article also gives a classification of metals according to the intensity of transfer immediately after grinding and removal of metal adhesions. The influence of metal and the depth of micro-scratching on the morphology of the wear site is shown. It was found that molybdenum, having a low adhesive activity to silicon carbide, is able to penetrate microcracks and other surface defects during micro-scratching. The width of microcracks and the depth of metal penetration were determined

Crystallographic texture of hot rolled uranium-molybdenum alloys

The uranium molybdenum (U-Mo) alloys have potential to be used as low enriched uranium nuclear fuel in research, test and power nuclear reactors. U-Mo alloy with composition between 7 and 10 wt% molybdenum shows excellent body centered cubic phase (γ phase) stabilization and presents a good nuclear fuel testing performance. Hot rolling is commonly utilized to produce parallel fuel plate where it promotes the cladding and the fuel alloy bonding. The mechanical deformation generates crystallographic preferential orientation, the texture, which influences the material properties. This work studied the texture evolution in hot rolled U-Mo alloys. The U7.4Mo and U9.5Mo alloys were melted in a vacuum induction furnace, homogenized at 1000°C for 5 h and then hot rolled at 650°C in three height reductions: 50, 65 and 80%. The crystalline phases and the texture were evaluated by X-ray diffraction (XRD). The as-cast and processed alloys microstructures were characterized by optical and electronic microscopies. The as-cast, homogenized and deformed alloys have γ phase. It was found microstructural differences between the U7.4Mo and U9.5Mo alloys. The homogenized treatment showed effective for microsegregation reduction and were not observed substantial grain size increasing. The deformed uranium molybdenum alloys presented α, γ, θ texture fibers. The intensity of these texture fibers changes with deformation step.

High-temperature oxidation of Moss—Mo3Si alloys doped with Sc or Y in air and in a steam-air mixture

For continuation of investigations aimed at studying the effect of rare earth elements (RRE) on the behavior of metal-silicide molybdenum alloys in oxidizing environments, the results of experimental modeling of high-temperature oxidation of alloys based on Mo—15 (at.%) Si and doped with Sc or Y in the isothermal mode in the air and in a steam-air environment are presented. New data on the effect of REE on oxidation resistance of alloys of the Mo—Si system of hypoeutectic composition, the formation of scale on their surface, the phase composition and the structure of oxidation products was obtained.

Heat Transfer, Molten Pool Flow Micro-Simulation, and Experimental Research on Molybdenum Alloys Fabricated via Selective Laser Melting

Molybdenum-based alloys fabricated via selective laser melting are considered to represent the next generation of high-temperature structural materials, but the additive manufacturing technology aiming at refractory alloys has not been explored extensively. Multi-field coupling simulation can be used as a practical tool to simulate a single track of molybdenum alloy printed via selective laser melting, observe the topography of the molten pool over time, and determine the effect of Marangoni flow on defect suppression. In this study, the tmelt, tvapor, and the competition mechanism of spreading/solidification time were considered, the dominant spreading time was calculated, and a reasonable process parameter window for fabricating molybdenum alloy was obtained. It was found that keeping the energy density in the range of 3.1 × 1011 J/m3–4.0 × 1011 J/m3 could better maintain appropriate melt channel depth and width and was beneficial to the droplet spreading behavior. This range was deemed suitable for printing molybdenum alloy.

Assessment of Electrochemical Compatibility of Structural Materials of some Dental Products

Orthopedic treatment of tooth anomalies in children and adolescents is provided the long-term use of various metal constructions and devices in the oral cavity – braces, retreaders, locks or rings with struts, wire arches, and so on. They are usually made of corrosion-resistant metals and alloys, most often they are made of stainless chromium-nickel austenitic steels of Х18Н9Т type (import analogue – steel 304), martensitic 08Х17 (import analogue – steel 430), nickel-titanium or nickel-molybdenum alloys. The main disadvantage of all metal products is their manifestation of electrochemical properties and participation in electrochemical processes which can flow into the oral cavity and provoke galvanoses, especially for their joint use. In the "in vitro" conditions, according to a specially developed method, investigations of electrode potentials of directly 4 types of very small (2–3 mm) orthodontic products, in recommended for such products environment were carried out: 3 % solution of sodium chloride (pH=6,8), 2 % solution of citric acid (pH=0.5) and 2 % solution of baking soda (pH=8.65). It is found that the considered elements of orthodynamic systems have similar values of electrode potentials in neutral and weakly-alkaline environments and, accordingly, in the absence of other metal inclusions in the oral cavity, can be used jointly without the risk of galvanosis. The most heterogeneous construction is an individual ring with a strut, in which the difference in the values of the potentials between the individual parts in the acidic medium is more than 120 mV, which is a prerequisite for increasing the likelihood of galvanosis. For simultaneous use of other elements, in particular standard doping brackets, the value of EMF can increase up to 160 mV.