Solidification and processing of aluminium based immiscible alloys

Copyright @ 2009 TMSThe Al-Sn and Al-Pb based immiscible alloys have significant potential for bearing applications. However, the mixing and understanding of solidification process for immiscible alloys have been long standing challenges for their development. This paper presents solidification and microstructural evolution of the Al-Sn-Cu alloys and also describes the mechanism of effective mixing by the intensive shearing. The experimental work was also focused on analyzing the effects of shear rate, temperature and time on Sn droplets size and their distribution. Results have been compared with earlier study on Al-Si-Pb alloys. Experimental results suggest that the intensive shearing process produces homogeneous and finely dispersed Sn and Pb droplets.This work was funded by the EPSRC and DTI

Засоби систем захисту доступом та модель класифікації рівнів захисту

We use Kieffer's model to represent the vibrational density of states (VDoS) and thermodynamic properties of pure substances in pressure-temperature space. We show that this model can be simplified to a vibrational model in which the VDoS is represented by multiple Einstein frequencies without significant loss of accuracy in thermodynamic properties relative to experimental data. The resulting analytical expressions for thermodynamic properties, including the Gibbs energy, are mathematically simple and easily accommodated in existing computational software for making thermodynamic databases. We show for aluminium, platinum, orthoenstatite and forsterite that thermodynamic properties can be represented with comparable accuracy as with Kieffer's model with the same number of fitting parameters as in the Mie-Grüneisen-Debye model. We demonstrate that the method enables to achieve thermodynamic properties with superior accuracy relative to the Mie-Grüneisen-Debye method. The method is versatile in the sense that it allows incorporating dispersion of Grüneisen parameters. It is possible to extend the formalism to include other physical effects, such as intrinsic anharmonicity in the same way as in vibrational models based on Kieffer's formalism

Segregation of Yttrium at the Mg/MgO interface in an Mg-0.5Y Alloy

Interfacial segregation of selected elements can be exploited to manipulate the potency of solid substrates for heterogeneous nucleation, thus controlling the solidification process. As the native inclusions in Mg alloys, MgO acts as the nucleating substrate, but it has rarely been studied in terms of its interactions with alloying elements. In this work, investigations of yttrium (Y) segregation at interfaces between native MgO particles and Mg in an Mg-0.5Y alloy were carried out by state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM) and associated spectroscopy. Experimental results show that native MgO particles in Mg-0.5Y possess two typical morphologies: truncated octahedron primarily faceted by {111}MgO and minorly by {100}MgO, and cubic shape with unique {100}MgO facets. Y atoms are found to segregate at both Mg/{111}MgO and Mg/{100}MgO interfaces, leading to the formation of two different 2-dimensional compounds (2DCs). The 2DC at the Mg/{111}MgO interface is identified as two atomic layers of a face-centered cubic Y2O3 phase in terms of crystal structure and chemistry, whilst it is an Mg(Y)-O monolayer at the Mg/{100}MgO interface, coherently matching with the terminating {100}MgO plane. Discussion is focused on the mechanisms underlying the formation of the 2DCs, their effects on the nucleation potency of MgO particles, and grain refinement. This work sheds light on how heterogeneous nucleation can be manipulated by altering the nucleation potency of a substrate through deliberately promoting elemental segregation of carefully chosen element(s)

Segregation of Yttrium at the Mg/MgO interface in an Mg-0.5Y Alloy

Supplementary materials are available online at https://www.sciencedirect.com/science/article/pii/S1359645423004780#sec0023 .Copyright © 2023 The Author(s). Interfacial segregation of selected elements can be exploited to manipulate the potency of solid substrates for heterogeneous nucleation, thus controlling the solidification process. As the native inclusions in Mg alloys, MgO acts as the nucleating substrate, but it has rarely been studied in terms of its interactions with alloying elements. In this work, investigations of yttrium (Y) segregation at interfaces between native MgO particles and Mg in an Mg-0.5Y alloy were carried out by state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM) and associated spectroscopy. Experimental results show that native MgO particles in Mg-0.5Y possess two typical morphologies: truncated octahedron primarily faceted by {111}MgO and minorly by {100}MgO, and cubic shape with unique {100}MgO facets. Y atoms are found to segregate at both Mg/{111}MgO and Mg/{100}MgO interfaces, leading to the formation of two different 2-dimensional compounds (2DCs). The 2DC at the Mg/{111}MgO interface is identified as two atomic layers of a face-centered cubic Y2O3 phase in terms of crystal structure and chemistry, whilst it is an Mg(Y)-O monolayer at the Mg/{100}MgO interface, coherently matching with the terminating {100}MgO plane. Discussion is focused on the mechanisms underlying the formation of the 2DCs, their effects on the nucleation potency of MgO particles, and grain refinement. This work sheds light on how heterogeneous nucleation can be manipulated by altering the nucleation potency of a substrate through deliberately promoting elemental segregation of carefully chosen element(s).EPSRC under grant number EP/N007638/1. The SuperSTEM Laboratory is the U.K National Research Facility for Advanced Electron Microscopy, supported by EPSRC under grant number EP/W021080/1. SHW gratefully acknowledges the China Scholarship Council (CSC) for financial support

Анализ основных показателей годовой финансовой отчетности предприятия

Актуальность темы обусловлена необходимостью постоянного мониторинга показателей финансовой отчетности с целью координирования деятельности компании. Объектом исследования в данной работе является ООО "РСТ". Предмет исследования – анализ финансовой отчетности ООО "РСТ". Цель выпускной квалификационной работы – анализ основных показателей годовой финансовой отчетности ООО "РСТ" и определение направлений совершенствования внутренней и внешней политики.The relevance of the topic is due to the need for constant monitoring of financial reporting indicators in order to coordinate the company's activities. The object of research in this paper is LLC "RST". The subject of the study is the analysis of the financial statements of LLC "RST". The purpose of the final qualification work is to analyze the main indicators of the annual financial statements of LLC "RST" and identify areas for improving domestic and foreign policy

Assessment techniques, database design and software facilities for thermodynamics and diffusion

The purpose of this article is to give a set of recommendations to producers of assessed thermodynamic data, who may be involved in either the critical evaluation of limited chemical systems or the creation and dissemination of larger thermodynamic databases. Also, it is hoped that reviewers and editors of scientific publications in this field will find some of the information useful. Good practice in the assessment process is essential, particularly as datasets from many different sources may be combined together into a single database. With this in mind, we highlight some problems that can arise during the assessment process and we propose a quality assurance procedure. It is worth mentioning at this point, that the provision of reliable assessed thermodynamic data relies heavily on the availability of high quality experimental information. The different software packages for thermodynamics and diffusion are described here only briefly

Solidification of Al-Sn-Cu based immiscible alloys under intense shearing

The official published version of the Article can be accessed from the link below - Copyright @ 2009 The Minerals, Metals & Materials Society and ASM InternationalThe growing importance of Al-Sn based alloys as materials for engineering applications necessitates the development of uniform microstructures with improved performance. Guided by the recently thermodynamically assessed Al-Sn-Cu system, two model immiscible alloys, Al-45Sn-10Cu and Al-20Sn-10Cu, were selected to investigate the effects of intensive melt shearing provided by the novel melt conditioning by advanced shear technology (MCAST) unit on the uniform dispersion of the soft Sn phase in a hard Al matrix. Our experimental results have confirmed that intensive melt shearing is an effective way to achieve fine and uniform dispersion of the soft phase without macro-demixing, and that such dispersed microstructure can be further refined in alloys with precipitation of the primary Al phase prior to the demixing reaction. In addition, it was found that melt shearing at 200 rpm and 60 seconds will be adequate to produce fine and uniform dispersion of the Sn phase, and that higher shearing speed and prolonged shearing time can only achieve minor further refinement.This work is funded by the EPSRC and DT

Relationship between polarities of antibiotic and polymer matrix on nanoparticle formulations based on aliphatic polyesters

In the field of nanomedicine, nanoparticles are developed to target antibiotics to sites of bacterial infection thus enabling adequate drug exposure and decrease development of resistant bacteria. In the present study, we investigated the encapsulation of two antibiotics with different polarity into different PEGylated polymeric nanoparticles based on aliphatic polyesters, to obtain a better understanding of critical factors determining encapsulation and release. The nanoparticles were prepared from diblock copolymers comprising of a poly(ethylene glycol) block attached to an aliphatic polyester block of varying polarity: poly(lactic-co-glycolic acid) (mPEG-PLGA), poly(lactic-co-hydroxymethyl glycolic acid) (mPEG-PLHMGA) and poly(lactic-co-benzyloxymethyl glycolic acid) (mPEG-PLBMGA). Hydrophobic bedaquiline and hydrophilic vancomycin were encapsulated via single and double-emulsion solvent evaporation techniques, respectively. Encapsulation, degradation and release studies at physiological simulating conditions were performed. Drug polarity and preparation techniques influenced encapsulation efficiency into polymer nanoparticles, giving almost complete encapsulation of bedaquiline and approx. 30% for vancomycin independent of the polymer type. The nonpolar bedaquiline showed a predominantly diffusion-controlled release independent of polymer composition. However, polar vancomycin was released by a combination of diffusion and polymer degradation, which was significantly affected by polymer composition, the most hydrophilic polymer displaying the fastest release