Papers by Keyword: Beryllium

Abstract: Due to their properties, potential for demonstrating shape memory behavior, and cheaper cost, copper-based SMA materials hold great promise for use in a variety of industrial and medical applications. This work used powder metallurgy to create Cu-based SMA using Cu-25Zn-4Al as the master alloy. The master alloy having Beryllium additions of (0.4, 0.8, and 1.2%wt.) was studied. After combining the powders, all samples were compacted using compaction stresses of (800 MPa). Then, the process of sintering in a tube furnace using argon gas has been accomplished in three stages, the first stage lasting two hours at 350°C, the second lasting two hours at 550°C, and the third lasting three hours at 900°C. All samples are treated with a solution heat treatment that involves heating them to 850 °C for an hour, quenching them quickly in saline ice water, and then aging them at 450 °C for 180 minutes. According to linear polarization tests the adding 1.2 weight percent of the Be to the base alloy (Cu-25Zn-4Al alloy) decreased corrosion rate by (95%) as compared to the base sample in a 3.5 weight percent NaCl solution. Keywords-Cu-Zn-Al shape memory alloys, corrosion behavior, shape memory properties, Beryllium, microstructure

Abstract: For the first time, the time dependences of the temperature of aluminum, zinc and zinc-aluminum alloys alloyed with II A group elements under spontaneous cooling mode were obtained; an anomalous course and two characteristic times of the cooling process were found, and their mechanism was explained; the temperature dependence of the thermophysical properties of the investigated metals and alloys was established; the temperature dependence of the coefficients of convective heat transfer and radiation of Al, Zn and Zn55Al and Zn5Al alloys was experimentally determined; the influence of the concentration of II A group elements and temperature on the heat capacity and thermodynamic functions of Zn55Al and Zn5Al alloys was revealed.

Abstract: The effect of beryllium hardening has been studied. Beryllium is sintered by method of hot isostatic pressing (HIP), depending on the temperature of powders pressing. The research results of electron microscopic studies were the base for demonstrating formation of the hydraulic phase at the grain boundary of sintered beryllium and influence of the reinforcing phase on the mechanical properties of the HIP blank. The dependence of beryllium precision elastic limit and conventional yield strength from the size of the reinforcing particles of beryllium oxide has been found. The obtained equation provides a description of the “dispersion-grain-boundary" mechanism of isostatic pressed Beryllium hardening.

Abstract: As a special functional and structural material, the rare metal beryllium has been widely applied in many key areas due to its excellent nuclear properties, optical properties and physical properties such as low density, high specific stiffness, high specific strength, and excellent thermal properties. This article systematically reviews application of beryllium in strategic nuclear energy, high-energy physics, inertial navigation systems, aircraft structural components, optical systems and commercial fields. The paper also examines how beryllium promoted technological advances and improved the facilities performance in its applications fields. Beryllium plays an important role in the development of nuclear technology, defense, and aerospace, which make beryllium become a strategic and critical engineering material. The paper provides a reference for scientists and technicians to employ beryllium in more fields.

Abstract: In this communication, the use of gallium nitride doped with beryllium as an efficient converter for white light emitting diode is proposed. Until now beryllium in this material was mostly studied as a potential p-type dopant. Unfortunately, the realization of p-type conductivity in such a way seems impossible. However, due to a very intensive yellow emission, bulk crystals doped with beryllium can be used as light converters. In this communication, it is demonstrated that realisation of such diode is possible and realisation of a colour rendering index is close to that necessary for white light emission.

Abstract: For polycrystalline Beryllium (Be) specimens, data of yield strength, ultimate strength, elastic modulus, inelastic secant modulus elongation and grain size were obtained by using of material testing machine and metaloscope. It showed that: elastic modulus, inelastic secant modulus were basically independent with grain size; ultimate strength appeared at the end of tension process; relation between rate of yield strength to ultimate strength and elongation was found to be linear, but this rate had no clear correlation with grain size; relation between strength (yield, ultimate) and grain size was satisfied with Hall-Petch equation. Based on test data and analysis above, a bilinear model was given to simulate stress-strain constitutive behavior; an equation expressing relation between elongation and grain size was also derived.

Abstract: The Young’s modulus and internal friction of Be polycrystals (grain sizes 6-60 μm) prepared with a powder metallurgy technique were studied acoustically in both amplitude independent and-dependent damping ranges. The measurements were made by composite oscillator at resonant frequencies of longitudinal vibrations of about 100 kHz in the temperature range of 100-873 K. The data were used to get information about micro-flow properties at vibration stresses of 0,2-30 MPa. It was found that the micro-flow diagrams became non-linear at amplitudes higher than 5 MPa. Mechanical properties (acoustic micro-flow stress σ_y, yield point σ_0.2 and ultimate strength σ_В) as functions of grain size have shown clearly a correlation in the framework of Hall and Petch law at room temperature but this similarity is not complete: stresses σ_0.2 and σ_В are one order of magnitude higher and change more steeply with grain size as compared to σ_y. The similarity is not observed for the temperature dependences. The values of σ_0.2(Т) and σ_В(T) decrease smoothly at higher temperatures but σ_у(Т) demonstrates an unusual minimum at ~400 K. The different behavior of the acoustic and mechanical stresses proves, evidently, that the ultrasonic energy losses and the flow stress level are due to the different nature of obstacles for the vibration (near equilibrium positions) and translation movement of dislocations in beryllium.

Abstract: In order to evaluate the fracture characteristic near the crack tip of beryllium specimen, beryllium compact tension specimen with plane strain state is designed. The stress distribution near the crack tip is measured at different loading level by X3000 stress analyzer. Moreover, a finite element model for calculated the stress and strain fields in beryllium compact tension specimen has also been set up. As a result, the stress and strain distribution near the crack tip at different loading has been calculated by this model. According to the critical tension loading of beryllium specimen, the maximum plastic strain and the radius of the plastic zone near the crack tip are determined, where the maximum plastic strain near the crack tip is about 0.018 and the maximum radius of plastic zone is about 0.3mm. Altogether, the fracture toughness of beryllium is obtained, which is about 19.1MPam1/2.

Abstract: This work studies the deformation mechanisms active in two pure hexagonal close packed metals, beryllium (Be) and zirconium (Zr), during equal channel angular extrusion processing. An experimental-theoretical approach is employed to assess their relative contributions through measurement and calculation of texture evolution. A new multi-scale constitutive model, incorporating thermally activated dislocation density based hardening, is shown to effectively predict texture evolution as a function of processing route, number of passes (up to four), initial texture, pressing rate, and processing temperature. Texture predictions are shown to be in very good agreement with experimental measurements. Also, it is found that the two most active deformation modes in Be are basal slip and prismatic slip, where the predominant one is interestingly found to depend on die angle. Deformation in Zr during the first pass is predicted to be accommodated not only by its easiest mode, prismatic slip, but by basal slip and tensile twinning.

Abstract: Beryllium (Be) is susceptible to introduce stress because it is a brittle metal with a high elastic modular. The compact tension (CT) specimens of beryllium were designed to determinate stress and fracture behaviors. Stress distribution near notch in CT beryllium was measured by the combination of an X-ray stress analysis and a custom-designed load device. The results show that local stresses near notch tip are much higher than those on other area. Thus, stress concentration lead the CT specimens fracture along the notch direction. Residual stresses due to machining are remained. A finite element ( FE ) calculation on the same loaded geometry was made, and the result is agreement with the measured stress distribution near notch.