Search Results for eutectic point

This article begins with a schematic illustration of a eutectic system in which the two components of the system have the same crystal structure. Eutectic systems form when alloying additions cause a lowering of the liquidus lines from both melting points of the pure elements. 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. It concludes with a discussion on terminal solid solutions.

This article illustrates the equilibrium phase diagram for an aluminum-silicon system, showing the metastable extensions of 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.

This article presents the binary eutectic phase diagram to understand the various structures that evolve in a binary eutectic system during solidification. It describes the various classifications and solidification principles of the eutectic structures. The formation of halos in eutectic microstructures of most alloy systems is also discussed.

This article describes the various specimen preparation procedures for lead, lead alloys, and sleeve bearings, including sectioning, mounting, grinding, polishing, and etching. The microscopic examination and microstructures of lead and lead alloys are discussed. The article also provides information on the microstructures of sleeve bearing materials.

From the point of view of economics and ecology, thin-wall ductile iron (TWDI) castings can compete in terms of mechanical properties with the light castings made of aluminum alloys. This article discusses the effect of technological factors on the cooling rate and physicochemical state of the liquid metal for preparing thin-wall castings with good mechanical properties and performance while avoiding casting defects. It describes a variety of defects that may appear during the production of TWDI castings, such as casting skin anomalies (e.g., flake graphite, graphite segregation), graphite clusters, exploded graphite, slag inclusions, shrinkage porosity, eutectic chill and secondary carbides, and cold shuts. The article reviews the tensile, fatigue, impact, and wear properties of TWDI castings. It provides information on the production and applications of TWDI castings.

This article describes different methods by which the composition of cast iron can be analyzed. It provides particular emphasis on the methods for evaluating the graphitization potential of a melt with prescribed limits on carbon, silicon, and alloying elements. The article discusses the effect of cooling rate on the graphitization of a given composition by chill and wedge tests. Thermal analysis of cooling curves gives excellent information about the solidification and subsequent cooling of cast iron alloys. The article presents some applications of the cooling curve analysis and explains the evaluation of carbon-silicon contents, graphite shape, graphite nucleation, and contraction-expansion balance. It illustrates the use of an immersion steel sampling device for compacted graphite iron production and provides information on the ferrite-pearlite ratio in ductile iron.

This article introduces basic physical metallurgy concepts that may be useful for understanding and interpreting variations in metallographic features and how processing affects microstructure. It presents some basic concepts in structure-property relationships. The article describes the use of equilibrium binary phase diagrams as a tool in the interpretation of microstructures. It reviews an account of the two types of solid-state phase transformations: isothermal and athermal. The article discusses isothermal transformation and continuous cooling transformation diagrams which are useful in determining the conditions for proper heat treatment (solid-state transformation) of metals and alloys. The influence of the mechanisms of phase nucleation and growth on the morphology, size, and distribution of grains and second phases is also described.

Alloy phase diagrams are useful for the development, fabrication, design and control of heat treatment procedures that will produce the required mechanical, physical, and chemical properties of new alloys. They are also useful in solving problems that arise in their performance in commercial applications, thus improving product predictability. This article describes different equilibrium phase diagrams (unary, binary, and ternary) and microstructures, description terms, and general principles of reading alloy phase diagrams. Further, the article discusses plotting schemes; areas in a phase diagram; and the position and shapes of the points, lines, surfaces, and intersections, which are controlled by thermodynamic principles and properties of all phases that comprise the system. It also illustrates the application of the stated principles with suitable phase diagrams.

The control of the solidification process of cast iron requires understanding and control of the thermodynamics of the liquid and solid phases and of the kinetics of their solidification, including nucleation and growth. This article addresses issues that allow for the determination of probability of formation and relative stability of various phases. These include the influence of temperature and composition on solubility of various elements in iron-base alloys; calculation of solubility lines, relevant to the construction of phase diagrams; and calculation of activity of various components. It discusses the role of alloying elements in terms of their influence on the activity of carbon, which provides information on the stability of the main carbon-rich phases of iron-carbon alloys, that is, graphite and cementite. The article reviews the carbon solubility in multicomponent systems, along with saturation degree and carbon equivalent.

This article describes the liquidus plots, isothermal plots, and isopleth plots used for a hypothetical ternary phase space diagram. It discusses the single-phase boundary (SPB) line and zero-phase fraction (ZPF) line for carbon-chromium-iron isopleth. The article illustrates the Gibbs triangle for plotting ternary composition and discusses the ternary three-phase phase diagrams by using tie triangles. It describes the peritectic system with three-phase equilibrium and ternary four-phase equilibrium. The article presents representative binary iron phase diagrams, showing ferrite stabilization (iron-chromium) and austenite stabilization (iron-nickel).

Directed-energy deposition (DED) is a kind of additive manufacturing (AM) technology based on synchronous powder feeding or wire feeding. This article provides a comprehensive coverage of DED for ceramic AM, beginning with an overview of DED equipment setup, followed by a discussion on DED materials and the DED deposition process. The bulk of the article is devoted to the discussion on the microstructure and properties of oxide ceramics, namely alumina and zirconia ceramics.

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 the nucleation of the austenite-flake graphite eutectic, austenite-spheroidal graphite eutectic, and austenite-iron carbide eutectic. The article provides a discussion on primary austenite and primary graphite. It also describes the growth of eutectic in cast iron in terms of isothermal solidification, directional solidification, and multidirectional solidification.

This article reviews the fundamental solidification concepts for understanding microstructural evolution in fusion welds. The common concepts, namely, nucleation, competitive grain growth, constitutional supercooling, solute redistribution, and rapid solidification, depend on the solidification parameters during welding, are discussed. The article discusses important solidification parameters, including temperature gradient, solid/liquid interface growth rate, and cooling rate.