The superplastic behavior of ultrafine-grained (UFG) alloys Al-6% Mg-0.12% Sc-0.10% Zr-0.1% X, where X = Yb (alloy 1 (Yb)), Er (alloy 2 (Er)), and Hf (alloy 3 (Hf)), was studied. The objects of comparison were alloys Al-6% Mg-0.12% Sc-0.20% Zr (alloy 4 (Zr)) and Al-6% Mg-0.22% Sc-0.10% Zr (alloy 5 (Sc)). The effect of a simultaneous increase in the flow stress and elongation to failure in the superplasticity mode has been found. The maximum elongation to fracture in UFG alloys 1 (Yb) and 2 (Er) is observed at lower deformation temperatures than in alloys 4 (Zr) and 5 (Sc). The superplastic characteristics of alloy 3 (Hf) exceed those of alloys 4 (Zr) and 5 (Sc) with an increased content of alloying elements (in at %). UFG alloy 1 (Yb) at low temperature (400 degrees C) has good ductility (delta = 910%). The effect of the type and concentration of alloying elements on the deformation behavior and grain growth in UFG alloys Al-6% Mg is analyzed. With the superplasticity of UFG alloys, there is competition between strain-induced grain growth and dynamic recrystallization. It is shown that the fracture of UFG alloys under superplasticity is caused by the formation of pores on large Al3X particles.

The aim of this study was to investigate the effect of the Sc/Zr ratio (Sc/Zr = 0.45–2.2) on the intergranular corrosion (IGC) resistance of Al–Mg alloys with different Mg content (2.5, 4, and 6%) and with a Sc + Zr = 0.32%. A change in the Mg concentration led to a change in the number of β-phase particles. A change in the Sc/Zr ratio led to a change in the composition of Al3(Sc,Zr) particles. The IGC resistance of Al–Mg–Sc–Zr alloys was investigated by Tafel electrochemical tests and stationary tests. It has been demonstrated for the first time that two types of IGC defects appear during electrochemical tests. Large Type I defects were associated with the destruction of primary β-phase particles located along the dendrite boundaries. Fine Type II defects were associated with the grain boundaries (GBs). It has been demonstrated that during the stationary tests, Type I defects are formed. ECAP and subsequent annealing affect the ratio of the number of Type I and II defects. Increasing the Sc/Zr ratio reduced the depth of Type I defects, increased the fraction of Type II defects, and reduced the corrosion current density icorr. It has been shown for the first time that the dependence of icorr(T) had a three-stage character with a maximum at 450 °C in alloys with 2.5% and 4% Mg. A two-stage dependence of icorr(T) is observed in alloys with 6% Mg. Increasing icorr at T < 450 °C is due to the precipitation of the secondary β-phase particles on Al3(Sc,Zr) particles and due to the effect of solid-phase wetting of the GBs by β-phase, which leads to an increase in the proportion of GBs containing thin layers of β-phase. Decreasing icorr at T > 450 °C is associated with the dissolution of β-phase particles.

Al-6%Mg-Sc-Zr alloys with the total ratio of Sc + Zr = 0.32 wt.% make up the target of this research. The content of scandium and zirconium varied with an increment of 0.02%. The alloys were produced by induction casting. Their ultrafine-grained (UFG) microstructure was formed with Equal Channel Angular Pressing (ECAP). Such cast alloys have a homogeneous macrostructure formed by small equiaxed grains in the central part of the ingot and columnar crystals along the edges of the cross section. After ECAP, the average grain size in the alloy specimens is 0.5–1 µm. The average grain size does not depend on the ratio of Sc and Zr in these alloys. Superplasticity tests were performed at temperatures ranging from 300 to 500 °C and at a strain rate varying between 3.3·10-3 and 3.3·10-1 s-1. UFG Al-6%Mg-0.20%Sc-0.12%Zr and Al-6%Mg-0.18%Sc-0.14%Zr alloys exhibit the highest superplasticity. It was suggested that changes in Sc:Zr ratio affect spatial distribution and composition of the following precipitating particles: Al3Sc, Al3Zr, Al3(ScxZr1-x). An increase in Zr concentration is shown to reduce the susceptibility of UFG alloys to cavitation fracture.

The process of precipitation of Al3Zr particles in cast Al–(0.25–0.4) wt

The results of the studies of the corrosion resistance of Al–Mg alloys with different contents of magnesium and different ratios of scandium and zirconium (Sc : Zr) have been presented. The alloys have been obtained using induction casting. The effect of the annealing temperature on the microhardness and specific electrical resistivity of cast Al–Mg–Sc–Zr alloys has been studied. Electrochemical corrosion tests were performed in an environment simulating intergranular corrosion in aluminum alloys. It has been shown that an increase in the content of magnesium results in an increase in the corrosion current, and a decrease in the content of scandium (under the condition of Sc + Zr = const) results in a decrease in the rate of intergranular corrosion. It has been established that the dependence of the corrosion current density on the annealing temperature of Al–Mg–Sc–Zr alloys with an increased Sc : Zr ratio exhibits a non-monotonic pattern with a maximum.

We consider a mathematical model of a planar Mach–Zehnder interferometer with nonideal beam splitters. For this model, we obtain two fidelity estimates of the matrix–vector multiplication in the form of dependences of the multiplication error on the beam splitting error in directional couplers. The first estimate is obtained as a measure of the difference between the transfer matrices implemented by interferometers and is presented in the form of the norm of the difference between two unitary matrices corresponding to ideal and non-ideal interferometers. The second estimate is obtained as a measure of the difference in output intensities. It is shown that in the latter case the fidelity depends both on the beam splitter error and on the parameters of the input signals. We verified the second estimate using computer simulations of MZI in COMSOL Multiphysics.

The aim of the study is to develop a methodology for assessing changes in the microstructure of aluminum under dynamic deformation in a rather wide range of the strain rate and strain degree. The distribution of the microstructure and the strength properties in the cross-section of pure aluminum samples (A99) after dynamic deformation according to the Taylor test were studied. The tests were carried out at room temperature using a PG-20 light-gas cannon, at sample throwing speeds of 127 and 165 m/sec. An interference microscope (Leica IM DRM) and a scanning electron microscope (Jeol JSM-6490) were used to study the aluminum microstructure; the microhardness measurements were carried out on an HVS-1000 device to study the uniformity of the strain distribution in samples. It is shown that three characteristic areas can be distinguished in aluminum samples after Taylor test: the elastic deformation zone, the plastic deformation zone, and the zone of severe plastic deformation, which is located in the area of collision of the sample with a steel barrier. It is shown that dynamic deformation reduced the grain structure from 1 – 1.1 mm to 2.5 – 3 μm at high impact velocities. An elongated grain shape is observed in the collision zone. The proposed method provided determination of the critical strain degree necessary for the onset of grain fragmentation and allowed us to explain the formation of zones of weak and severe plastic deformation. It is shown that the critical strain degree corresponding to the beginning of grain fragmentation increases from 0.18 to 0.21 with an increase in the throwing speed of the sample from 127 to 165 m/sec. In the zone of weak deformation, plastic deformation proceeds by intragrain riveting and the initial stages of grain fragmentation. In the zone of severe plastic deformation, a fine-grained microstructure is formed, which leads to an increase in the microhardness of aluminum in accordance with the Hall – Petch equation.

The thermal stability of a bimetallic wire made of three novel aluminum alloys Al–0.25 wt

The results of investigations of the corrosion resistance of Al-Mg-Sc-Zr alloys with varying Mg content and different Sc/Zr ratios are presented. The objects of investigations were the Al-Mg-Sc-Zr alloys with total Sc + Zr content of 0.32 wt the increments of 0.02 wt effect of annealing temperature on the microhardness and electrical resistivity of the Al-Mg-Sc-Zr alloys was investigated. Corrosion tests were carried out in a medium simulating intergranular corrosion in aluminum alloys. Electrochemical studies and mass loss tests were performed. An increase in the Sc concentration and a decrease in the Zr one were shown to result in an increase in the corrosion rate. The primary Al3(ScxZr1-x) particles were found to have the main effect on the corrosion resistance of Al-Mg-Sc-Zr alloys. The dependence of the corrosion current on the annealing temperature of the Al-Mg-Sc-Zr alloy was found to have a non-monotonous character (with a maximum).

Results of investigations of the kinetics of solid solution decomposition during annealing of fine-grained (FG) Al–0.5

Superplastic behavior of ultrafine-grained (UFG) Al-6Mg-0.12Sc-0.10Zr-0.1X alloys, where X = Yb (Alloy #1-Yb), Er (Alloy #2-Er), and Hf (Alloy #3-Hf), has been studied. The total content of Sc, Zr, Yb, Er, Hf in the alloys was 0.32 wt. Al-6Mg-0.12Sc-0.20Zr (Alloy #4-Zr) and Al-6Mg-0.22Sc-0.10Zr (Alloy #5-Sc). Their UFG microstructure was formed with ECAP. Two different types of deformation behavior during superplasticity were demonstrated. A simultaneous increase in yield stress and elongation to failure during superplastic deformation was discovered. High deformation temperatures were shown to cause a competition between dynamic (strain-induced) grain growth and dynamic recrystallization, leading to a finer grain microstructure. The values of strain hardening factor (n), strain rate sensitivity factor (m), and superplastic deformation threshold stress (Sp) were determined. The impact of the type and concentration of alloying elements on the deformation behavior and dynamic grain growth of Al-6 that the maximum elongation to failure in Alloy #1-Yb and Alloy #2-Er is observed at lower deformation temperatures than in Alloy #4-Zr and Alloy #5-Sc. The superplastic properties of Alloy #3-Hf are superior to those of Alloy #4-Zr and Alloy #5-Sc with high content of alloying elements (in at. manifests good elongation to failure (910 satisfiability of Hart's criterion for calculating uniform deformation value under superplastic conditions was verified. It was demonstrated that cavitation when pores are formed in large Al3X particles at high temperatures causes early failure of aluminum alloys.

The nucleation of the Al3X (X = Zr, Yb, Er, Hf) particles in the cast conductor Al alloys including the alloys additionally doped with Mg and Si was studied. The alloys were made by induction casting. To investigate the particle nucleation kinetics, the specific electrical resistivity (SER) and microhardness measurements were applied. It was shown that the investigated alloys can be subdivided into three groups. Group I includes the alloys, which the decrease in the SER with increasing annealing temperature takes place in due to the particle nucleation. Group II includes the alloys, which the particle nucleation takes place in during the bulk crystallization. The SER magnitude of such alloy was close to the SER of pure Al. The SER of the alloys of Group III almost doesn’t change during annealing and is 3.0-3.4 ·cm that evidences a high alloy solid solution stability. Using Jonhnson-Mehl-Avrami-Kolmogorov equation, the particle nucleation kinetics in the Group I alloys was analyzed. The activation energy of the particle nucleation in the Group I alloys was found to be close to the activation energy of volume diffusion, but the values of the decomposition intensity coefficient (n = 0.5-0.8) in Johnson-Mehl-Avrami-Kolmogorov equation appeared to be smaller that the theoretical value n = 1.5 typical for the particle nucleation inside the bulk crystal lattice. This contradiction was related to the presence of large primary or eutectic Al3X particles in the alloy structure. The Al-0.25%Zr-0.25%Er-0.15%Si alloy was shown to have the optimal set of properties: the characteristics of this alloy after annealing match the requirements to the alloys being developed: SER less than 2.95 ·cm, microhardness Hv ~ 550 MPa.

The thermal stability of a bimetallic wire made of four novel aluminum alloys Al – 0.25 % Zr with different Sc and Hf contents has been investigated. A wire made of pure aluminum A99 was studied as an object of comparison. Alloys were obtained by injection molding in vacuum. Cast samples were subjected to severe plastic deformation and annealing, which ensured the formation of a uniform microstructure and the release of stabilizing Al3(Zr,Sc,Hf) nanoparticles. The wire ∅ 0.26 mm was obtained by joint deformation of an aluminum alloy with a copper shell by rolling in rolls. The effect of 30-minute annealing in the temperature range from 200 to 500 °C on the parameters of the microstructure and physical and mechanical properties (microhardness, strength, plasticity, specific electrical resistivity) of the wire was studied. The wire has high strength and increased thermal stability. After annealing at a temperature of 500 °C, a homogeneous fine-grained structure with a grain size of 3 – 5 µm was formed in the wire, increased hardness and strength of the samples was observed due to the separation of Al3(Zr,Sc,Hf) particles. There is an intense diffusion of copper from the shell into the surface layers of the aluminum alloy, which can lead to embrittlement of the wire.

In this paper, we propose a method for predicting the refractive index variation in InGaAlAs tunnel-coupled quantum wells under the action of an electric field. Complex of mathematical and experimental studies to optimize the heterosystems design forthe semiconductor modulator construction according to a planar Mach-Zehnder interferometer scheme is demonstrated.

The thermal stability of a composite wire made of microalloyed aluminum alloys Al–Zr–(Sc, Hf) is investigated. The wire is produced by the combined drawing of a copper-coated aluminum alloy. The effect of annealing on the mechanical properties of the composite conductive aluminum wire is studied. It is shown that the process of decomposition of the solid solution upon the annealing of composite wires occurs in two stages, due to the separate precipitation of Al3Zr particles at “low” temperatures and the precipitation of Al3(Sc, Hf) particles at “high” annealing temperatures. Mechanical tensile tests show that annealing at 500°C for 30 minutes reduces the strength and increases the ductility of the wire by up to 10%. After annealing, a homogeneous fine-grained structure is formed in the wire, and increased hardness and strength of the samples is observed due to the release of Al3(Sc, Hf) particles.

In this paper, we propose a method for predicting the refractive index variation in InGaAlAs tunnel-coupled quantum wells under the action of an electric field. Complex of mathematical and experimental studies to optimize the heterosystems design forthe semiconductor modulator construction according to a planar Mach--Zehnder interferometer scheme is demonstrated. Keywords: Mach--Zehnder modulator, nanoheterostructure, quantum mechanical calculations, refractive index, transmission electron microscopy, photoelectric spectroscopy.

The work presents the results of studies of the structure and microhardness during annealing of cast and microcrystalline (MC) Al–2.5%Mg–Sc–Zr alloys with a total Sc and Zr content of 0.32%. The Sc content varies from 0.1 to 0.22% with an interval of 0.02%, and the Zr concentration in the alloy changes proportionally. In the initial state, the cast alloys are characterized by a homogeneous coarse-grained macrostructure. MC alloys are obtained by equal-channel angular pressing (ECAP) and have a homogeneous fine-grained structure in the initial state. The temperature of the beginning of recrystallization of MC alloys is determined. The mechanisms and temperature of the beginning of solid-solution decomposition in the cast and MC alloys are determined according to the Johnson–Mehl–Avrami–Kolmogorov model. It is found that the partial replacement of scandium with zirconium leads to a steady increase in the thermal stability of solid solution of Sc and Zr in aluminum.