Experimental studies of density and viscosity of gallium-rare-earth metal composition alloys with light lanthanides (neodymium and samarium) are investigated for the first time. It is established that these compositions are characterized by long-term non-monotonic changes of properties (relaxation processes) in liquid state. The coefficients of temperature expansion of Ga95Nd5 and Ga97Sm3 alloys and activation energy of viscous flows of their melts are calculated based on experimental data.

Obtaining amorphous alloys with good mechanical and anticorrosion properties is an important problem of modern condensed matter physics. Since the preparation of amorphous alloys involves casting them from liquid state, information on the properties of the melts is needed. Viscosity is one of the most informative structure-sensitive property of melts. In this paper viscosity of some glass-forming Al-Ni-Co-Nd(Sm) melts with different ratio of transition metals was studied using damped oscillation method in a wide temperature range up to 1550 K. Activation energies of the viscous flow were calculated from the experimental data. The hysteresis of viscosity temperature dependences during heating and subsequent cooling was found. It can be associated with a melt transition to a more homogeneous state. The repeated heating and cooling of the melts without crystallization lead to Arrhenius type of viscosity temperature dependences.

The long-term relaxation of large-scale heterogeneities in aluminum–rare earth metal (REM) melts with a REM content of 5–10 at

Electrical resistivity of Co 48 Fe 25 Si 4 B 19 Nb 4 amorphous alloy and with small additions of rare-earth metals ( = Nd, Sm, Tb, Yb) was studied using the AC four-probe method. It was found that these alloys have a specific behavior of electrical resistivity after crystallization-temperature dependences of resistivity at cooling are non-linear and can be fitted as ln R~ T -1/4 . Keywords: amorphous alloys, metallic glasses, electrical resistivity, rare-earth metals.

Abstract—Aluminum-based glass-forming alloys are actively studied due to their low specific weight and high mechanical and corrosion properties. Viscosity (Shvidkovsky method), density (gamma absorption method), and electrical resistivity (contactless method in rotating magnetic field) of a Al91La9 glass-forming alloy are experimentally studied in a wide temperature range. Measurements have been carried out in a high-purity helium atmosphere. Samples are prepared by arc melting in a high-purity helium atmosphere. Chemical analysis of the composition is performed using an inductively coupled plasma atomic emission spectrometer. The morphology of the formed compounds is analyzed using a scanning electron microscope. The elemental compositions of regions in different contrasts are determined using X-ray spectral microanalysis. The phase composition is studied using X-ray diffraction (CuKα). It is shown that the alloy is characterized by a hysteresis (discrepancy of heating and subsequent cooling polytherms) of the properties and long-term transitions to a more homogeneous state (long-term relaxation). These processes are observed in viscosity and density but are not detected upon measuring electric resistivity. Therefore, we assume that they do not influence the local order in the melt and occur at a meso- or macroscopic scale.

Equiatomic Al-Ni-Co-Cu-Zr alloy was produced by arc melting. Rapidly quenched rods were prepared by suction casting method. Density, electrical resistivity and thermal analysis of the alloy were investigated experimentally. Basing on X-ray diffraction it was shown that the structure of the alloy consists of two competing solid solutions: BCC-ZrNi2Al (Heusler-type phase) and & gamma;-phase Cu9Al4. In addition, pure cooper and Cu3Al, Cu5Zr7Ni5 intermetallic compounds were determined. Rapid quenching of this alloy leads to the formation of solid solutions based on BCC-ZrNi2Al and high-temperature Cu3Al phase. It is shown that the alloy in crystalline state has a linear density change up to solidus temperature. A region of resistivity decrease with increasing temperature is found out for the first time. The melting process goes in a wide temperature range (above 250 K) where 4 thermal reactions were detected. Density and electrical resistivity changes here non-linearly. In liquid state there are no thermal effects in the alloy and temperature dependencies of density and electrical resistivity can be fitted by linear functions.

Long-term relaxation of large–scale inhomogeneities in aluminum – rare earth metal melts with a content of the latter in the range of 5–10 at % was previously observed when measuring viscosity and density, but did not manifest itself when measuring electrical resistance and magnetic susceptibility. This behavior could be related both to the specifics of the measured properties and to the size of the samples, which in the case of viscosity and density is much larger: 12–15 g with a diameter of a cylindrical crucible ~15 mm for viscosity and density, and less than 1 g with a crucible diameter of 6 and 4 mm for electrical resistance and magnetic susceptibility, respectively. To solve this problem, the time dependences of the electrical resistance of the Al91La9 melt were measured at 1060°C for samples of various sizes by the rotating magnetic field method, namely for standard (crucible diameter of 6 mm) and enlarged (crucible diameter of 10.5 mm) When the sample increases, the random measurement error increases, so additional measures had to be taken to stabilize the current in the coils, creating this field. It was found that with an increase in the mass of the sample to 2.15 g with a crucible diameter of 10.5 mm the large-scale heterogeneity that occurs during the melting process is manifested. It is interpreted as a compact “cloud” of intermetallic microparticles surrounded by a melt with a high content of REM. The sample relaxes to an equilibrium homogeneous state in a few hours. To speed up the process, additional exposure is required – heating to a high temperature, about 1500°C, which reduces the time to less than one minute. At the same time, in small (0.7 g with a crucible diameter of 6 mm) samples, the mentioned heterogeneity does not occur. The probable cause of the inhomogeneity is the flow of REM atoms to the surface and the reverse flow of aluminum atoms into the volume during crystallization, which is similar to liquation during the crystallization of cast iron and steel. The measurements carried out allow us to estimate the scale of the resulting inhomogeneities, which corresponds to the size of the enlarged sample.

Electrical resistivity of Co48Fe25Si4B19Nb4 amorphous alloy and with small additions of rare-earth metals (R = Nd, Sm, Tb, Yb) was studied using the AC four-probe method. It was found that these alloys have a specific behavior of electrical resistivity after crystallization - temperature dependences of resistivity at cooling are non-linear and can be fitted as lnR ~ T-1/4.

Eutectic alloys, due to their low melting point, are promising materials for the production of metal glasses. Unlike crystalline alloys, amorphous alloys have no long-range order, which leads to an increase in hardness, mechanical strength, corrosion resistance and magnetic permeability. The main criterion for the application of amorphous materials in practice, under which the formation of a single-phase metallic glass during quenching, is the critical diameter. Therefore, an urgent task in this area of research is to increase the critical diameter of current amorphous alloys. One of the methods of improving the glass-forming ability of alloys is their dilution with more refractory metals. In this paper, we present amorphous metallic glasses of (Co41Fe7Cr15Mo14C15B6)100 – xRx alloys with dilution with rare earth metals (R = Gd, Ho, La, Nd, Y, Yb; x = 0; 2). The critical diameter, phase and elemental composition of the alloys depending on the quenching rate were determined by X-ray diffraction and scanning electron microscopy. It is shown that the addition of 2 at. % Gd, Ho and Y significantly increases the glass-forming ability of the Co–Fe–Cr–Mo–C–B alloy. By spinning method, when quenched on an aluminum disk rotating at a linear speed of 11.5 m/s, tapes with a thickness of 19 to 73 microns were obtained. Rare inclusions with a high content of rare earth elements up to 35 at % were found on the surface of the tapes, which can act as crystallization centers.

This research discusses the static and dynamic analysis of the landing gear structure of an unmanned aerial vehicle (UAV). The dimensional study is conducted to investigate the effect of landing gear dimension variation on UAVs’ static strength and dynamic response. Static analysis was performed with Finite Element Method (FEM) software. The dynamic response of the UAV is analyzed using a single-degree-of-freedom vibration model. Based on the static analysis results, the landing gear stiffness and strength can be increased by increasing the width and decreasing the height, radius, and length of the landing gear structure. The energy dissipation in the dynamic analysis is described by hysteresis and viscous damping model. The dynamic response simulation results show that the increase in the stiffness of the landing gear leads to an increase in force transmission and acceleration of the UAV. Furthermore, the UAV response using the viscous damping model can accurately predict the system’s response with the hysteretic damping model for small damping conditions. However, the deviation was observed for large damping conditions.

Experimental investigations of density and electrical resistivity of Al86Ni6Co2R6 (R = Sm, Tb) alloys were carried out in a wide temperature range, including crystalline and liquid states. Density was measured by gamma-penetrating method, and electrical resistance – by contactless method in rotating magnetic field. The solidus and liquidus temperatures were determined, the coefficients of volume expansion and the relative changes in density and resistivity during melting were calculated. The molar volumes of the alloys were calculated. It was found that the alloys are characterized by a wide two-phase zone where density and resistivity dependences show nonlinear behavior. At liquidus temperature an abrupt increase in density and a decrease in electrical resistivity were found. It has been established that terbium increases density of the alloys and reduces their resistivity more than samarium. In liquid phase at temperatures below T = 1300–1350 K density hysteresis was detected, and its absence on resistivity curves was shown. This may indicate the processes of large-scale inhomogeneities decay that do not cause changes in the electronic subsystem of the alloys but play a significant role in amorphization. The revealed features of the properties will make it possible to optimize the process of melts preparing before rapid quenching in order to obtain high-quality amorphous and nanocrystalline samples.

Eutectic alloys, due to their low melting point, are promising materials for the production of metal glasses. Unlike crystalline alloys, amorphous alloys have no long-range order, which leads to an increase in hardness, mechanical strength, corrosion resistance and magnetic permeability. The main criterion for the application of amorphous materials in practice, under which the formation of a single-phase metallic glass during quenching, is the critical diameter. Therefore, an urgent task in this area of research is to increase the critical diameter of current amorphous alloys. One of the methods of improving the glass-forming ability of alloys is their dilution with more refractory metals. In this paper, we present amorphous metallic glasses of (Co41Fe7Cr15Mo14C15B6)100 – xRx alloys with dilution with rare earth metals (R = Gd, Ho, La, Nd, Y, Yb; x = 0; 2). The critical diameter, phase and elemental composition of the alloys depending on the quenching rate were determined by X-ray diffraction and scanning electron microscopy. It is shown that the addition of 2 at. % Gd, Ho and Y significantly increases the glass-forming ability of the Co–Fe–Cr–Mo–C–B alloy. By spinning method, when quenched on an aluminum disk rotating at a linear speed of 11.5 m/s, tapes with a thickness of 19 to 73 microns were obtained. Rare inclusions with a high content of rare earth elements up to 35 at % were found on the surface of the tapes, which can act as crystallization centers.

In present work, experimental studies of viscosity, density, and electrical resistivity of Al91Ce9 and Al90Sm10 glass-forming alloys are carried out. It is shown that these compositions are characterized by the presence of long-term processes of transition to a more homogeneous state (long-term relaxation).

Form-Finding Technique (FFT) is an optimization method developed to control the geometric shape of the structure. Through FFT, it is possible to change the initial shape of the structure to the final form with minimum critical working stress under a particular loading. This paper is aimed to investigate the effectiveness of FFT in designing the rear landing gear of fixed-wing Unmanned Aerial Vehicles (UAV). There are three parts of the study that will be done. The first part is how to find the best form of the rear landing gear with high strength through FFT. For this purpose, a computer program based on static linear analysis of 3D frame elements is developed, then the optimization function based on minimum strain energy has been added into the program to reduce the working bending stress to the minimum one. The second part is how to determine the stiffness, maximum strength, and absorbed energy of the optimized landing gear when the UAV touches the ground during landing. Another computational program based on the nonlinear finite element program has been developed to determine those parameters. The third part is how to determine the dynamic responses of the UAV under a shock load, which occurs in landing. For this purpose, the UAV with the rear landing gear is modeled as a spring-mass system. The stiffness of the spring is taken from the result of the second part. In general finding, it has been justified that the optimized form of the rear landing gears shows better behaviors than the initial model, showing the effectiveness of FFT when applied in designing landing gear.

It is shown that stable large-scale heterophase formations similar to clouds can exist in a system with phase separation outside the two-phase region on the concentration–temperature diagram and near its boundary. Such formations have a finely dispersed second phase. The applicability of this result to eutectic systems is discussed.

Aluminum-containing amorphous and nano-crystalline alloys, especially compositions with transition and rare-earth metals, are being intensively investigated over the last years due to their high service properties. This paper studies thermophysical properties (density and electrical resistivity) of Al86Ni6Co2R6 (R = Nd, Gd, Yb) glass-forming compositions in a wide temperature range, including the liquid state. It is found that the behavior of crystalline alloys is typical for aluminum compositions, namely: the linear decrease in density and the growth in electrical resistivity with increasing temperature. It is shown that these compositions are characterized by a wide two-phase region, whereas a transition to the liquid state at the liquidus temperature is accompanied by an abnormal density growth and electrical resistivity reduction. For the first time, it is found that the melt overheating up to 1350 K leads to the density hysteresis, which probably indicates to the fracture of large-scale inhomogeneity in melts.