Papers by Keyword: Zirconium

Abstract: The mechanical properties of anodic oxide films of Nb, Ta and Zr were studied by the nanoindentation method. Anomalously high elastic recovery after deformation was observed for oxides with thickness of 20 nm. An analogue of this behavior can be elastic membrane fixed on soft base that does not prevent the membrane from bending. Increase of the oxide thickness to 300 nm reduced the effect associated with the high elasticity of oxide and easy deformation of the soft metal substrate, and was accompanied by an increase in the plastic component of deformation, which is similar to the behavior of ceramic materials with low elastic and significant residual plastic deformation.

Abstract: In this study, activation energies required for the static recrystallization behavior during the annealing process after cold deformation of Al-Mg-Si alloy to which zirconium was added in various proportions were investigated. Depending on the zirconium content, the activation energies of the alloys were found and compared both experimentally and by calculation. For this purpose, alloys containing 0.1, 0.2 and 0.3 wt-% Zr were cold rolled after taking into solution and quenching. And then, the alloys were annealed at 375 °C and 500 °C for different annealing times. After the alloys were prepared metallographically, their grain structures were examined microscopically. Depending on the temperature, recrystallization-% was found by image analysis and experimental recrystallization-% curves were drawn. The time taken for recrystallization-50% to experimentally find the activation energy required for recrystallization to occur was found from the curves. These values were replaced in the relevant formulations and the required activation energy was experimentally found from the slope of the Arrhenius equation and the ln t_50% and 1/T graph. In order to find the recrystallization-% by calculation, the nucleation rate and growth rate of the new recrystallized grains were found by image analysis. By substituting these values in Johnson-Mehl-Avrami equation, the calculated recrystallization-% curves of the alloys were found. From here, using the relevant equations, Arrhenius equation was passed and the activation energy was calculated from the slope of ln k and 1/T graph. The results showed that the activation energy increased with the increase of the zirconium ratio, and even the most effective zirconium ratio was between 0.1-0.2% by weight in increasing the activation energy. Therefore, this ratio should be considered in processes where recrystallization, which also affects other properties of the alloy, is not desired.

Abstract: Zirconium alloys are used in the nuclear industry due to their low neutron capture cross-section and resistance to corrosion, irradiation and creep. The microstructure of the nuclear fuel components evolves during the manufacturing route and can impact the subsequent processes or the final properties. Thus, numerical modeling of thermo-mechanical manufacturing processes is of interest to understand and master these microstructure evolutions.Numerical modeling of thermo-mechanical manufacturing processes with FORGE^® NxT software is applied. These models provide the thermo-mechanical history of the material at each integration point of the finite element (FE) mesh, which can be used to assess locally the continuous dynamic and post-dynamic recrystallization during hot extrusion.Mean-field models were developed in Python and integrated into FORGE^® NxT software, to quantify the microstructure evolution at the macro-scale of the component. Full-field models (DIGIMU^® software¹) were also developed for considering microstructural heterogeneities and the influence of initial microstructure at the mesoscopic scale while improving the mean-field equations by homogenization.After validation based on experimental results, these two recrystallization models provide complementary information to optimize the process parameters at the macro-scale and to better understand mesoscopic scale phenomena, such as:• At the macro-scale: influence of hot extrusion parameters on the continuous dynamic and post-dynamic recrystallization of Zircaloy-4.• At the meso-scale: influence of the initial microstructure on the recrystallization phenomena with improved precision. Indeed, the topology of the microstructure is predicted and not only the mean values/distributions of the state variables.

Abstract: 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

Abstract: The main difficulty in obtaining adapters from stainless steel + zirconium metal combination lies in the formation of fragile intermetallic compounds at the weld border. By its properties, zirconium is very close to titanium, and therefore the manufacture of tubes from this combination, as well as pure titanium, is considerably difficult. Optimum explosion welding parameters have been developed, ensuring the highest adhesion strength compared to the existing production methods. At the weld border, a structure characteristic of compounds of dissimilar metals was revealed. The permissible heating temperatures for this combination are determined. The fundamental possibility of using the explosion energy as a factor stimulating the connection of dissimilar metals in order to obtain high-quality multilayer tubes, billets and products for various purposes is demonstrated, resulting in the introduction of environmentally friendly technology. Economic analysis of the manufacturing technology of bimetallic tubes by welding explosion was carried out. The cost-effectiveness of manufacturing technology of bimetallic stainless steel + zirconium metal compound nozzles, which is based on the use of high-pressure gradients and loading velocities to create production, was evaluated.

Abstract: Computer simulation of the process of ingotless rolling-extruding (IRE) of aluminum alloy rods with a content of 0.15% zirconium in the Deform 3D software package performed. The temperature, speed and deformation parameters of the treatment of the investigated alloy determined under different process conditions. To check the adequacy of the models, rod samples were made on a CRE-200 laboratory unit at specified processing parameters. Using the Deform 3D software package, the forces acting on the rolls and the extruding die during the IRE determined and their comparison with tensometric experimental data presented. The mechanical properties, electrical resistivity of semi-finished products after processing by the method of ingotless rolling-extruding and for conditions of their heating to 230 °C investigated. Technological recommendations for the manufacture of deformed semi-finished products using the method of ingotless rolling-extruding are proposed.

Abstract: The article presents the investigation results of the structure and properties of rods of aluminum alloys containing zirconium, cerium and lanthanum after ingotless rolling-extruding (IRE) and heat treatment. The patterns of changes in the microstructure, mechanical properties, electrical resistivity depending on the chemical composition of the alloys, processed by the IRE method and various modes of rods annealing are shown. A metallographic analysis of the grain structure of the samples in a deformed state and after annealing performed. The temperatures at which the alloy structure remains stable and maintains the level of operational properties revealed. The effect of chemical composition on the heat resistance of deformed semi-finished products represented. The study made it possible to evaluate the level of properties of experimental alloys after processing by the method of ingotless rolling-extruding and various modes of rods annealing.

Abstract: Various bioceramic materials including zirconia and hydroxyapatite have been developed for various applications. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) is one of the most interesting features of calcium phosphate-based bioceramic that widely used in various applications especially for bio-application, bone engineering, and dentistry. However, the applications of pristine HAp have limited due to low load bearing applications. The wet chemical precipitation techniques was used to synthesize the solids based on zirconia. Hydroxyapatite and zirconia powder (0-30 weight %) were mixed homogeneously. Structure and morphological were characterized by SEM JEOL-JSM-T330A. The presence of functional group was observed by FTIR. Hardness value of material was measured by using Vickers hardness test measurement. Through this techniques, pure hydroxyapatite precipitate was obtained. Sintering temperature is an important factor that could influence the hardness of zirconia-doped hydroxyapatite. Based on the SEM observation, zirconia-doped hydroxyapatite were developed in blended morphology. FTIR results shows the interaction between hydroxyapatite and zirconia. Increasing zirconia increased the hardness value of zirconia-doped hydroxyapatite. Eventually, these ceramic-based materials could be developed for dental materials applications.

Abstract: This article presents the results of the study of the joint effect of the processing conditions of the new composition of the Al-Zr system alloy by combined casting and rolling-extruding and two-stage annealing on the structure and properties of round bars used in the manufacture of heat-resistant wires. The research show patterns of changes in the properties, the specific electrical resistance of the bars, depending on different conditions of deformation and heat treatment of aluminum alloy with a content of 0.3% zirconium and 0.2% iron. The results of micro-X-ray spectral analysis and the granular structure of the samples before and after two-stage annealing confirming the stability of the structure after heating and preserving the strength of semi-finished products. Presented parameters of combined casting and rolling-extruding and two-stage annealing for the manufacture of rods from the studied alloy make it possible obtaining good combination of mechanical properties and electrical conductivity.

Abstract: The crystal structures of the binary compounds ZrAl₃ and HfAl₃ at 600°C belong to the structure type ZrAl₃ (Pearson symbol tI16, space group I4/mmm, a = 4.00930(11), c = 17.2718(7) Å for ZrAl₃ and a = 3.9849(3), c = 17.1443(15) Å for HfAl₃). Substitution of Ge atoms for Al atoms in ZrAl₃ and HfAl₃ led to the formation of the ternary compounds ZrAl_2.52(1)Ge_0.48(1) and HfAl_2.40(1)Ge_0.60(1), respectively, where the latter is probably part of a solid solution extending from the high-temperature modification of HfAl₃. The crystal structures belong to the tetragonal structure type ht-TiAl₃ (tI8, I4/mmm, a = 3.92395(11), c = 9.0476(4) Å for ZrAl_2.52Ge_0.48 and a = 3.9021(2), c = 8.9549(8) Å for HfAl_2.40Ge_0.60). The structure types ZrAl₃ and ht-TiAl₃ are both members of the family of close-packed structures.