Origin of microstructure in faceted/nonfaceted eutectic alloys

by Simin D. Bagheri

Publisher: National Library of Canada = Bibliothèque nationale du Canada in Ottawa

Written in English
Published: Downloads: 72
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Edition Notes

SeriesCanadian theses = Thèses canadiennes
The Physical Object
FormatMicroform
Pagination2 microfiches : negative.
ID Numbers
Open LibraryOL14778032M
ISBN 100315785772
OCLC/WorldCa30071917

The alloy composition had a significant influence on the oscillation behavior, and the oscillations were found to increase as the compositions deviated from the eutectic composition. The regime of banded structures was established for the carbon tetrabromide-hexachloroethane system, and a conceptual model is presented for the formation of bands. In the first part of the experiment, an investment casting shell mold system, produced for NiAl alloys, was used and investigated for the NiAl-9Mo alloy in the industrial scale furnace. Due to the lower temperature gradient of ∼ K mm −1, the microstructure of the samples was dendritic. of as-DS Ag-Cu eutectic alloys were statistically analyzed and the results are summarized in Figure2f. The results show that the ELS of as-DS Ag-Cu eutectic alloys are about – nm (Figure2a–c). With increasing growth rate in the absence of a MF, the ELS of Ag-Cu alloys was gradually decreased by 32% from to nm. AIVTe–B2 IIITe3 eutectic alloys were synthesized, and their microstructure was analyzed. Attempts to prepare aligned eutectics by directional solidification resulted in anomalous eutectics, which is attributable to the polymorphism of the phases involved.

Cast iron exhibits a considerable amount of eutectic in the solid state. This article discusses the structure of liquid iron-carbon alloys to understand the mechanism of the solidification of cast iron. It illustrates nucleation of the austenite-flake graphite eutectic, austenite-spheroidal graphite eutectic, and austenite-iron carbide eutectic. In this study, A series of the high strength (T82Sn18)xNbx (x=0, 1, 3, 5, and 9 at%) ultrafine eutectic alloys with large plasticity are developed by suction casting method. The Ti82Sn18 binary eutectic alloy consists of a mixture of a hcp Ti3Sn and a α-Ti phases having the plate-like lamellar type duplex structure with micro scaled eutectic colony. The focus is on the two common magnesium alloy groups: Mg-Al alloys and Mg-Zn-rare earth alloys. The key elements described are: nucleation (including grain refinement), growth of the primary phase and the formation of the eutectic phases. Keywords: Directional solidification, Fe - C alloy eutectic, Microstructure, Longitudinal section, Transverse section 1. Introduction During the liquid/solid phase transformation examined eutectic alloys formed extensive range of different phase microstructures. Eutectic alloys attract attention in .

alloy. Microstructure formation is strongly influenced by the alloy composition, the growth rate and the local temperature gradient. Fortunately, this can usually be reduced to the study of two classes of microstructure corresponding to eutectic and dendritic (off-eutectic) alloys (Kurz and Fisher, ). Figure Lamellar eutectic structure found after application of high density pulsed electric current to eutectic Al-Si alloy. 30 Figure Optical photomicrographs of eutectic silicon particles in Al wt.% Si alloys without electric current application (a), with direct current application (b), and.   2. Theory. Consider a eutectic dendrite growing at a constant velocity V with a dendritic tip radius R against an incident flow of U in an undercooled bulk liquid. As shown in figure 1, lamellae of two eutectic phases, α and β, are perpendicular to the dendritic envelope from a local view and have a half width of S α and S β, ng that the interlamellar spacing λ is much. Microstructure of as-received samples. The substrate for laser surface remelting was arc cast with a composition of Al 81 Cu 13 Si 1 shows the SEM micrograph of the as received material and the EDX mapping of the primary elements, Al, Cu and Si. The SEM micrograph of the substrate revealed a ternary eutectic structure with θ – Al 2 Cu and Si phases dispersed uniformly in α – Al.

Origin of microstructure in faceted/nonfaceted eutectic alloys by Simin D. Bagheri Download PDF EPUB FB2

AbstractSpecimens of the K (77°C) ternary eutectic of the Bi–In–Sn system were solidified unidirectionally at very low speeds and quenched to form a representative solid/liquid interface for subsequent study.

From such interfaces, this eutectic was observed to be of the faceted–faceted–non-faceted type, freezing to form the phases Bi (faceted), BiIn (faceted), and γ-Sn, Cited by: The article describes the aluminum-silicon eutectic system and the lead-tin eutectic system.

It discusses eutectic morphologies in terms of lamellar and fibrous eutectics, regular and irregular eutectics, and the interpretation of eutectic microstructures.

The article examines the solidification of a binary alloy of exactly eutectic composition. For eutectic alloys with at least two phases, the microstructure may exhibit different kinds of morphologies, based on the alloy composition and the solidification condition.

The regular rod/lamellar microstructures are grouped into normal eutectics, while the broken-lamellar, irregular, complex-regular or quasi-regular eutectics are named Cited by:   Tensile Origin of microstructure in faceted/nonfaceted eutectic alloys book showed that the as-cast AlCoCrFeNi alloy possessed an excellent combination of high strength and high ductility owing to the uniform FCC(L1 2)/BCC(B2) lamellar microstructures.

Fig. 2 shows the tensile engineering and true stress–strain curves of the as-cast AlCoCrFeNi alloy. It is evident that the ultimate tensile stress was ± 50 MPa and the ductility Cited by:   T he effect of shear-induced convection on the solidification behavior and microstructural evolution of eutectic alloys has been a promising subject of many studies in the last several decades.

In the s, on the basis of Jackson and Hunt’s model,[] Verhoeven and Homer[] reported that the convective flow produced little effect on eutectic growth in the eutectic by: 7.

Thus, the observed good response [Fig. 2(a, b)] is due to the nature of faceted/ nonfaceted eutectic growth. It has, however, been shown [14] that dur- ing directional solidification of AI-Si alloys, there is a propensity for nucleation and growth of equiaxed eutectic grains ahead of an otherwise planar and directional eutec- tic front.

The results are compared with those previously obtained in the Fe-C and Fe-Fe3C alloys, the latter being shown to be an irregular eutectic despite the regularity of the microstructure. The alloy exactly at the eutectic at 12% Si would have neither the primary Si phase nor the primary Al phase, but only the eutectic structure throughout.

This is the theory according to the simple binary Al–Si phase diagram, but, in reality, it is more complicated, because of eutectic Si modifiers, faster cooling rates and the additions of.

This article focuses on the metallography and microstructures of wrought and cast aluminum and aluminum alloys. It describes the role of major alloying elements and their effect on phase formation and the morphologies of constituents formed by liquid-solid and/or solid-state transformations.

Volume 3 provides a complete explanation of phase diagrams and their significance and covers solid solutions; thermodynamics; isomorphous, eutectic, peritectic, and monotectic alloy systems; solid-state transformations; and intermediate phases.

Book. Full-text available (faceted–non-faceted) eutectic. Our dynamic and 3D synchrotron-based X-ray imaging results reveal the markedly different microstructural and, for the first time. aluminum macrostructure and microstructure occur simultaneously with the freezing, homogenization, preheat, hot or cold reduction, annealing, or solution or precipitation heat treatment of the aluminum alloy.

Good interpretation of microstructure relies on having a complete history. Fig. 2 shows the microstructure of the cross-sectional structure after laser cladding (laser scan velocity was 1 mm/s, single layer).

Fig. 2(a) is the overall morphology of the cladding layer, the cladding height was about 1 mm, Fig. 2(b) shows the microstructure at the bottom of the cladding layers, there was coarse α-Ni columnar dendrites and regular lamellar eutectic in this area, most of. Growth of faceted/nonfaceted eutectic structures There exist many remaining questions regarding faceted/nonfaceted eutectic alloys although they have been extensively used in the industry.

The goal of this project is to investigate and characterize various microstructures obtained in Cu-B and AMPD-SCN systems employing different compositions. This article illustrates equilibrium phase diagram for the aluminum-silicon system showing metastable extensions of the liquidus and solidus lines.

It describes the classification and microstructure of the aluminum-silicon eutectic. The article presents the theories of solidification and chemical modification of the aluminum-silicon eutectic.

A general feature of faceted-nonfaceted eutectic systems is that both primary phases can appear in the microstructure, one phase forming a halo around the second.

The haloes of the nonfaceted phase about the faceted phase in hyper- eutectic alloys are more extensive than those of the faceted phase about the nonfaceted phase in hypoeutectic alloys. The solidification of binary eutectic alloys produces two-phase composite materials in which the microstructure, that is, the geometrical distribution of the two solid phases, results from complex.

Al-Ni and Al-Ce Binary Eutectic Systems Previous researchers of the Al-Ni and Al-Ce binary systems observed fully eutectic microstructures at Alwt% Ni and Alwt% Ce, with volume fractions of intermetallics of approximately 8% and 15%, respectively. 69 Both binaries are of the faceted/non-faceted type and were observed to form.

A certain degree of cold working is advantageous in developing a fine microstructure with minute silicon crystals for eutectic and/or hypereutectic Al-Si cast alloys.

1. Introduction. Eutectic materials have been discovered in a batch of organic, metallic, semiconductors, crystalline oxides, and non-oxides.These materials can exhibit outstanding mechanical and functional properties because of their in-situ microstructures. Eutectics can exhibit a wide variety of geometrical arrangements, because they are composed of more than one phase.

The most common aluminum alloy systems are aluminum-silicon, aluminum-copper, and aluminum-magnesium. This article focuses on the grain structure, eutectic microstructure, and dendritic microstructure of these systems. It provides information on microsegregation and its problems in casting of alloys.

The relationship between remelting and undercooling in CoSi (at. %) eutectic alloys is investigated with in situ X-ray diffraction experiments.

Fig 2 shows the optical microstructures of LM 25 alloy with as-cast and T6 heat treatment produced by liquid metallurgical route. Figure 1 indicates three phases in the microstructure are α-Al primary, eutectic silicon and Mg 2 Si.

Eutectic was the combination of Al and Si phase microstructure that resulted from nucleation during solidification. Eutectics, peritectics and microstructure selection ↵ eutectic. The eutectic microstructure is also affected by the volume fractions of the two phases. The present section describes the observed morphologies for coupled growth, as shown schematically in.

The mechanical properties of Al–Si alloys are strongly related to the size, shape and distribution of eutectic silicon present in the microstructure In order to improve mechanical properties, these alloys are generally subjected to modification melt treatment, which transforms the acicular silicon morphology to fibrous one resulting in a noticeable improvement in elongation and strength.

The microstructure can be controlled by manipulating the speed of cooling the alloy, but this will be covered in the section on heat treatments. Eutectic Alloys First, consider the eutectic alloy of elements A and B as it is cooled from a temperature at location 1 to location 4 on the phase diagram.

High undercooling up to K was achieved in eutectic Ni Si alloy melt by using glass fluxing combined with cyclic superheating. A small quantity of amorphous phase was obtained in bulk. It can be concluded that the present MCA model can successfully predict the eutectic growth morphology in both regular non-faceted / non-faceted and irregular non-faceted / faceted eutectic alloy.

Evolution of the Eutectic Microstructure in Chemically Modified and Unmodified Aluminum Silicon Alloys by Hema V. Guthy A Thesis Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Master of Science in Materials Science and Engineering April APPROVED.

The microstructure of the eutectic alloy Fe30Ni20Mn35Al15 (in at.%) was modified by cooling at different rates from K, i.e., above the eutectic temperature.

The lamellar spacing decreased with increasing cooling rate, and in water-quenched specimens lamellae widths of ~ nm were obtained. The orientation relationship between the fcc and B2 lamellae was found to be sensitive to the.

In a previous lesson, I presented a eutectic diagram where a number of the compositions along the phase boundaries had been indicated. What I'd like to do here is to use that same data, and what I'm looking at is, in particular the eutectic alloy composition.

If I look at a temperature above the eutectic, I have essentially % liquid.eutectic growth; faceted / non-faceted (irregular composite in situ) crystallizing in such significant alloys as Fe-C and Al-Si has been presented. For the experimental verification of the elaborated model the results of the unidirectional crystallization of the irregular eutectic under in the Fe-C alloys were utilized.

Two-phase titanium alloys constitute very important group of structural materials used in aerospace applications [].Microstructure of these alloys can be varied significantly in the processes of plastic working and heat treatment allowing for fitting their mechanical properties including fatigue behaviour to the specific requirements [].The main types of microstructure are (1) lamellar.