Magnesium alloys are used in aircraft because of their light weight. However, for these alloys to be applied in electronic devices, high thermal conductivities are required. Several high-potential ...compositions of Mg–Zn–Y–Zr alloys were selected by phase composition and their freezing ranges calculated using Thermo-Calc software. The alloys were prepared, and their fluidity, hot tearing susceptibility, mechanical properties, and thermal conductivity were obtained and compared. The alloy composed of Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr was selected for further investigation, because of its high thermal conductivity and satisfactory mechanical properties. The Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr alloy's fluidity and hot tearing susceptibility were similar to those of the widespread AZ91 commercial casting magnesium alloy. The influence of a heat treatment regime on the microstructure, thermal conductivity, and mechanical properties of the developed alloy was also investigated. It was established that the room temperature thermal conductivity of the Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr alloy after aging at 300 °C for 5 h was 105 W/mK. Additionally, the following tensile test results were obtained in aged condition: 120 MPa yield strength, 200 MPa ultimate tensile strength, and 4% elongation. The utilization of solid solution heat treatment at 520 °C for 8 h prior to aging can promote up to 9% increase in elongation. The Mg–4 wt% Zn–3 wt% Y–0.3 wt% Zr casting alloy can be used as a high thermal conductivity material with industrial applications.
Magnesium alloys are commonly used to produce lightweight parts. While most magnesium alloys exhibit low thermal conductivities, high thermal conductivities are needed for electronic devices. In this ...study, we attempted to develop new magnesium casting alloys with high thermal conductivities. The MgZnSiCa alloy compositions were chosen using CALPHAD (CALculation of PHAse Diagrams) calculations, and alloy samples were prepared. The fluidity and hot-tearing resistance were measured. The results indicated that these properties were similar to those of AZ91 alloy. Tensile tests showed that high-pressure die casting could produce MgZnSiCa alloys possessing mechanical properties 1.5–3 times higher than those produced via sand casting. The alloy thermal conductivity was 126 W/mK at room temperature. The corrosion rates of the as-cast samples in NaCl/water solutions were two times higher than that of AZ91. Keywords: Magnesium alloy, Thermal conductivity, Phase composition, Corrosion rate, Sand casting, High-pressure die casting
A high resolution smoothing method is proposed for performing local estimates of the parameters of the Gutenberg-Richter law (GR). Using this method, the smoothing radius can be chosen large enough ...to ensure that the condition of applicability of GR law is met, while the distinguished areas of high activity align well with the distribution of epicenters and there is no “smearing” of narrow areas of really high seismic activity into wider zones, which are not actually active at the edges.
Effects of a liquid-phase sodium disilicate additive on the properties of ZrO2 ceramics containing 3 mol.% of Y2O3 and 2 wt% of Al2O3 are presented, including phase composition, microstructure, ...shrinkage, porosity, and bending strength. The distribution of elements along grain boundaries and the composition in a selected area of a lamella were investigated by transmission electron microscopy in pure and additive-containing samples. As a result of the introduction of the additive, sintering activity of the material increased, and the sintering temperature diminished down to 1150 °C. Thus, dense nanocrystalline materials with a crystallite size of 50–70 nm and a bending strength of up to 450 MPa were obtained. Optimized polymer-ceramic suspensions were used to produce objects with complex geometric shapes by 3D molding technology through layer-by-layer vat polymerization. According to in vitro assays, the obtained samples are nontoxic and cytocompatible with human osteosarcoma MG-63 cells, and according to in vivo experiments, are biocompatible and showing osseointegrative properties when implanted into the rat tibia.
Display omitted
•Introduction of a sodium disilicate in ZrO2 led to intensification of sintering.•Methyl methacrylate-based photopolymer resin were developed for DLP printing.•3D printed ZrO2 parts were cyto- and biocompatible, demonstrate the osteointegration.
Experimental investigation of the structure of a laser-induced spark emerging in the focusing of 50-ns radiation pulses is described. Two density jumps were discovered in the plasma of the ...laser-induced spark. One of them is localised in the vicinity of the focal plane of the lens, the other propagates from this plane in the laser propagation direction at a constant velocity of {approx}7.5 km s{sup -1}. (laser plasma)
We obtain inverse formulas for the Fourier coefficients of functions in the space of just meromorphic functions in the upper half-plane of complex variable. Both inverse and direct formulas can be ...interpreted as generalizations of the known Carleman formula.
Theorems establishing a connection between the type of an entire function and the distribution of its zeros play an important role in the theory of entire functions. The classical Lindelöf theorem ...asserts that zeros of an entire function of finite integer order and normal type possess a certain symmetry property. We prove counterparts of the Lindelöf theorem in the spaces of subharmonic functions in the complex plane and in the half-plane the growth of which is determined by the proximate order in the sense of Boutroux. The results are formulated in the terms of the upper density and the upper balance of the Riesz measure and the full measure of functions.
The spatiotemporal study of the diagram of laser radiation scattering by the laser-spark plasma produced by 3-ns and 50-ns pulses is performed. It is shown that radiation appearing outside the laser ...beam cone is scattered during the first one - two nanoseconds after the air breakdown, when the spark plasma is located in the vicinity of the laser beam waist and has a shape close to spherical.
We obtain counterparts of the Lindelöf theorem on types of entire functions whose growth is determined by the Boutroux proximate order. The results are formulated in terms of the upper density of ...zeros of a function and balance of its zeros.
We prove counterparts of the Lindelöf theorem in the spaces of entire functions and analytic functions in a half-plane the growth of which is determined by the proximate order in the sense of ...Boutroux.
PDF
