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thermal undercooling
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Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005207
EISBN: 978-1-62708-187-0
... model, free growth model, and constitutional undercooling model. The article concludes with a section on thermal analysis techniques for assessing grain-refining characteristics during master alloy processing. casting heterogeneous nucleation homogeneous nucleation nucleation kinetics...
Abstract
This article discusses selected highlights of thermodynamic relationships during solidification and nucleation kinetics behavior in connection with the basis of nucleation treatments, such as grain refinement and inoculation, to provide a summary of nucleation phenomena during casting. Nucleation during solidification is a thermally activated process involving a fluctuational growth in the sizes of clusters of solids. The article describes nucleation phenomenon such as homogeneous nucleation and heterogeneous nucleation. It discusses various grain refinement models, such as carbide-boride model, free growth model, and constitutional undercooling model. The article concludes with a section on thermal analysis techniques for assessing grain-refining characteristics during master alloy processing.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005217
EISBN: 978-1-62708-187-0
... Abstract Thermal analysis is a classical method of determining phase diagrams and can be used to analyze the deviation from solidification under equilibrium conditions. This article discusses the use of thermal analysis in industrial processes and in research. It describes the theoretical basis...
Abstract
Thermal analysis is a classical method of determining phase diagrams and can be used to analyze the deviation from solidification under equilibrium conditions. This article discusses the use of thermal analysis in industrial processes and in research. It describes the theoretical basis of simplified and differential thermal analysis. The article explains how to determine the liquidus and solidus temperatures by using cooling curves.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003195
EISBN: 978-1-62708-199-3
... heat-treating defects and how they can be controlled. It also presents an example to demonstrate how thermal and transformation-induced strains cause dimensional changes and residual stresses. continuous cooling transformation diagrams continuous heating transformation diagrams creep...
Abstract
This article presents an outline of the physical metallurgical principles that are associated with heat treating of steels. It describes the iron-carbon phase diagram and various types of transformation diagrams, including isothermal transformation diagrams, continuous heating transformation diagrams, and continuous cooling transformation diagrams. The primary design criteria for heat treating of steels this article covers are the minimization of distortion and undesirable residual stresses. The article presents the theoretical and empirical guidelines to understand sources of common heat-treating defects and how they can be controlled. It also presents an example to demonstrate how thermal and transformation-induced strains cause dimensional changes and residual stresses.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005240
EISBN: 978-1-62708-187-0
... thermophysical properties for pure metals and some commercial alloys, and tabulates enthalpy of fusion and the solidus and liquidus temperatures for various alloys of commercial interest. The article also tabulates density, thermal conductivity, surface tension, and viscosity for some commercial alloys...
Abstract
There are several main sources of thermophysical property data that provide the most authoritative and comprehensive compilations of critically and systematically evaluated data that are presently available. This article provides thermophysical property data to assist in the materials properties selection for the simulation of casting processes. The measurements of thermophysical property are difficult due to high temperatures and the reactivity of some alloys. The article discusses strategies adopted to minimize the effects of high temperatures and the reactivity of alloys. It presents thermophysical properties for pure metals and some commercial alloys, and tabulates enthalpy of fusion and the solidus and liquidus temperatures for various alloys of commercial interest. The article also tabulates density, thermal conductivity, surface tension, and viscosity for some commercial alloys.
Series: ASM Handbook
Volume: 4B
Publisher: ASM International
Published: 30 September 2014
DOI: 10.31399/asm.hb.v04b.a0005936
EISBN: 978-1-62708-166-5
... article also describes the generation of thermal, transformation, and hardening residual stresses. bearing steel case hardening distortion elastic plastic deformation heat treatment linear elastic deformation phase transformation quenching residual stress retained austenite steel...
Abstract
In the case of steels, heat treatment plays a fundamental role because no other process step can manipulate the microstructure in order to fulfill such a wide variety of possible in-service conditions. This article addresses heat treatment with regard to hardening and subsequent tempering of steel components in order to optimize tribological properties. It focuses on the heat treatment of tempering and bearing steels and on volume changes that take place due to phase transformations. Plastic deformations that occur due to shrinking and phase transformation are also discussed. The article also describes the generation of thermal, transformation, and hardening residual stresses.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005322
EISBN: 978-1-62708-187-0
... article provides a detailed account on thermal properties, conductive properties, magnetic properties, and acoustic properties of cast iron. It also discusses heat treatment, namely, stress relieving, annealing, normalizing, through hardening, and surface hardening. The article presents a discussion on...
Abstract
The term cast iron designates a group of materials that contain more than one constituent in their microstructure due to excess carbon that result in unique characteristics such as the fracture appearance and graphite morphology. This article discusses the classification of cast iron and the various metallurgical aspects, such as composition, alloying element, solidification, and graphite morphologies, of different types of cast iron. It describes the physical properties for various cast irons and the influence of microstructure and chemical composition on each property. The article provides a detailed account on thermal properties, conductive properties, magnetic properties, and acoustic properties of cast iron. It also discusses heat treatment, namely, stress relieving, annealing, normalizing, through hardening, and surface hardening. The article presents a discussion on the welding, machining and grinding, and coating of the types of cast iron.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005210
EISBN: 978-1-62708-187-0
... constitutional undercooling and interface energy. Since the thermal and solute gradients in the liquid are negative, constitutional supercooling will always be present to cause the interface to become unstable. The interface energy will initially stabilize the spherical nucleus, but the effect of interface...
Abstract
Nonplanar microstructures form most frequently during the solidification of alloys, and they play a crucial role in governing the properties of the solidified material. This article emphasizes the basic ideas, characteristic lengths, and the processing conditions required to control the columnar and equiaxed microstructures. The formation of cellular and dendritic structures in one- and two-phase structures is presented with emphasis on the effect of processing conditions and composition on the selection of microstructure and microstructure scales.
Series: ASM Handbook
Volume: 4E
Publisher: ASM International
Published: 01 June 2016
DOI: 10.31399/asm.hb.v04e.a0006271
EISBN: 978-1-62708-169-6
... be omitted as a separate step, and the simulation course only consists of thermal and mechanical simulation. Mechanical properties of the undercooled states are a necessary prerequisite for this model. Fig. 5 Simulation course of aluminum quenching with flow curves directly measured dependent...
Abstract
Heat treatment simulation helps to predict heat treatment results such as component microstructures, properties, residual stresses, and distortion, and thereby assists in reducing experimental effort in defining heat treatment parameters. This article discusses the modeling and simulation of age hardening as being the most important heat treatment to strengthen aluminum alloys. It provides information on the heat treatment simulation model, the yield strength model based on the responsible strengthening mechanisms, and the flow curve model based on mechanical tests. The article also discusses simulation of the quenching process, and provides examples for aluminum quenching simulation.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005209
EISBN: 978-1-62708-187-0
... z ′ Coordinate of specimen m ΔC o Solidus-liquidus interval at T s % Δ T o Solidus-liquidus interval ( T l − T s ) K δ C Solute diffusion length (D/ V ) m δ i Interface diffusion length (D i / V ) m δ K Capillary length (Γ/Δ T o ) m δ T Thermal length (Δ...
Abstract
One impressive example of plane front solidification (PFS) is the industrial production of large silicon single crystals, used mainly as substrates for integrated circuits. This article explores the PFS of a single phase, without taking convection into account. It discusses the solute build-up at the solid-liquid interface forming transients and steady state, the morphological stability/instability and perturbation theory, and rapid solidification effects, including solute trapping and oscillatory instabilities. The article presents a microstructural selection map that gives an overview of interface stability as a function of composition for a given alloy.
Book Chapter
Book: Alloy Phase Diagrams
Series: ASM Handbook
Volume: 3
Publisher: ASM International
Published: 27 April 2016
DOI: 10.31399/asm.hb.v03.a0006225
EISBN: 978-1-62708-163-4
... spacings of eutectics and eutectoids as a function of growth rate. Source: Ref 7 as published in Ref 6 The scale of the eutectic microstructure depends on the solidification rate, not directly on the cooling rate. The reason is that the thermal gradient has a negligible effect on the size of the...
Abstract
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.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005227
EISBN: 978-1-62708-187-0
... primary phase to nucleate at the particle surfaces. Thermal analysis showed that the unreinforced alloys exhibited undercooling for primary-phase nucleation, whereas the composites generally did not show any significant undercooling. The grain size of the composites is often smaller than that of the...
Abstract
This article discusses the solidification of matrix alloy in cast metal matrix composites (MMCs). It begins with a discussion on the mixing techniques in reinforcement incorporation and wettability of reinforcement. It describes the solidification processes, such as stir mixing and melt infiltration, used in the synthesis of MMCs. The article also discusses the fundamentals of solidification process and presents a computational modeling of particle/solidification front interactions in metal-ceramic systems. The article concludes with information on nanocomposites.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005226
EISBN: 978-1-62708-187-0
... of heat of fusion, solidification causes a large change in the thermal field, unlike solid-state transformation, where the enthalpy change on transformation is generally smaller. Thus, cooling rate prior to solidification is not a good predictor of metallurgical solidification processes. The...
Abstract
Rapid solidification is a tool for modifying the microstructure of alloys that are obtained by ordinary casting. This article describes the fundamentals of the four microstructural changes, namely, microsegregation, identity of the primary phase, identity of the secondary phase, and formation of noncrystalline phases. It considers three factors: heat flow, thermodynamic constraints/conditions at the liquid-solid interfaces, and diffusional kinetics/microsegregation, to understand the fundamentals of these changes. These factors are described in detail.
Book Chapter
Book: Alloy Phase Diagrams
Series: ASM Handbook
Volume: 3
Publisher: ASM International
Published: 27 April 2016
DOI: 10.31399/asm.hb.v03.a0006226
EISBN: 978-1-62708-163-4
.... From a technical viewpoint, the peritectic formation of austenite, γ, from primary ferrite, δ, is the most important peritectic reaction. Thermal analysis indicates that the reaction δ + L → γ proceeds to a great extent during continuous cooling, and δ-ferrite usually disappears completely on cooling...
Abstract
Similar to the eutectic group of invariant transformations is a group of peritectic reactions, in which a liquid and solid phase decomposes into a solid phase on cooling through the peritectic isotherm. This article describes the equilibrium freezing and nonequilibrium freezing of peritectic alloys. It informs that peritectic reactions or transformations are very common in the solidification of metals. The article discusses the formation of peritectic structures that can occur by three mechanisms: peritectic reaction, peritectic transformation, and direct precipitation of beta from the melt. It provides a discussion on the peritectic structures in iron-base alloys and concludes with information on multicomponent systems.
Book Chapter
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003107
EISBN: 978-1-62708-199-3
... often perform better that high-strength irons when these properties are important: Machinability Resistance to thermal shock Damping capacity Ability to be cast in thin sections Successful production of a gray iron casting depends on the fluidity of the molten metal and on the...
Abstract
This article provides information on the classification, microstructure, castability and section sensitivity of gray iron. It describes properties of the test bar and provides a short note on fatigue limit in reversed bending. Although the ASTM size B test bar is the bar most commonly used for all gray irons from classes 20 to 60, ASTM A 48 provides a series of bar sizes, and the user can select the bar sizes that best approximates the cooling rate in the critical section of the casting.
Book Chapter
Book: Alloy Phase Diagrams
Series: ASM Handbook
Volume: 3
Publisher: ASM International
Published: 27 April 2016
DOI: 10.31399/asm.hb.v03.a0006228
EISBN: 978-1-62708-163-4
...: 500×. Source: Ref 19 as published in Ref 1 Fig. 30 Same uranium-silicon alloy as Fig. 29 , but the casting has been thermally treated at 900 °C (1650 °F) for several hours. Structure is U 3 Si, within which are contained the remnants of U 3 Si 2 . Original magnification: 500×. Source...
Abstract
Eutectoid and peritectoid transformations are classified as solid-state invariant transformations. This article focuses primarily on the structures from eutectoid transformations with emphasis on the classic iron-carbon system of steel. It reviews peritectoid phase equilibria that are very common in several binary systems. The addition of substitutional alloying elements causes the eutectoid composition and temperature to shift in the iron-carbon system. The article graphically illustrates the effect of various substitutional alloying elements on the eutectoid transformation temperature and effective carbon content. The partitioning effect of substitutional alloying elements, such as chromium, manganese, and silicon, in pearlitic steel is also illustrated.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005236
EISBN: 978-1-62708-187-0
.... Nucleation is not included in the general framework of PF theory. Some authors ( Ref 12 , 27 ) propose models with strong thermal noise to introduce random nucleation in a PF simulation. However, it is well known that an interface in a well-resolved PF simulation needs a minimum of four to five numerical...
Abstract
Modeling of structure formation in casting of alloys involves several length scales, ranging from the atomic level to macroscopic scale. Intermediate length scales are used to define the microstructure of the growing phases and the grain structure. This article discusses the principles and applications of phase field method and cellular automaton method for modeling the direct evolution of structure at the intermediate length scales, where transport phenomena govern the spatial and temporal evolution of the structure that involves nucleation and growth.
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005406
EISBN: 978-1-62708-196-2
... enables a realistic PF simulation in technical alloys. Nucleation is not included in the general framework of PF theory. Some authors ( Ref 12 , 27 ) propose models with strong thermal noise to introduce random nucleation in a PF simulation. However, it is well known that an interface in a well...
Abstract
This article focuses on the intermediate length scales, where transport phenomena govern the spatial and temporal evolution of a structure. It presents the cellular automaton (CA) and phase field (PF) methods that represent the state of the art for modeling macrostructure and microstructure. The article describes the principles of the PF method and provides information on the applications of the PF method. The CA model is introduced as a computationally efficient method to predict grain structures in castings using the mesoscopic scale of individual grains. The article discusses the coupling of the CA to macroscopic calculation of heat, flow, and mass transfers in castings and applications to realistic casting conditions.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003171
EISBN: 978-1-62708-199-3
... has a velocity from the pouring operation. In addition, as the metal cools at the mold wall, thermal convection currents are set up at the mold wall, with the cooling metal traveling downward along the mold wall. These currents, combined with solutal convection and the residual liquid motion from...
Abstract
Solidification is a comprehensive process of transformation of the melt of metals and alloys into a solid piece, involving formation of dendrites, segregation which involves change in composition, zone formation in final structure of the casting, and microporosity formation during shrinkage. This article describes the imperfections in the solidification process including porosity, inclusions, oxide films, secondary phases, hot tears, and metal penetration. It talks about the purpose of the gating system and the risering system in the casting process.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005225
EISBN: 978-1-62708-187-0
... customers. The refined, high volume fraction of primary silicon yields a low coefficient of thermal expansion, low wear rate, and allows elevated-temperature operation. Silicon-aluminum alloys for thermal management in electronic packaging applications (Sandvik-Osprey, United Kingdom). Spray casting...
Abstract
Spray casting, also known as spray forming, is a niche casting process for the manufacture of preforms. This article lists commercial examples of alloys manufactured by spray casting and provides sequential steps of the spray casting process. Gas atomization is a chaotic, stochastic process that always produces a wide range of droplet diameters. The article schematically illustrates typical log-normal droplet diameter probability density distribution on a mass or volume basis obtained by gas atomization. It also illustrates the changes in solid fraction during the spray casting process as a function of axial distance from the point of droplet atomization. The article concludes with a section on occurrence of macrosegregation and coarsening in spray cast preforms.
Book Chapter
Book: Alloy Phase Diagrams
Series: ASM Handbook
Volume: 3
Publisher: ASM International
Published: 27 April 2016
DOI: 10.31399/asm.hb.v03.a0006222
EISBN: 978-1-62708-163-4
... entropy, a measure of the thermal energy unavailable for useful work. The Gibbs energy is defined as: (Eq 2) G = H − T S Because the enthalpy, H , at constant pressure is the heat content: (Eq 3) H = E + P V When dealing with liquids and solids, the PV term is usually very...
Abstract
This article begins with the one-component, or unary, diagram for magnesium. The diagram shows what phases are present as a function of the temperature and pressure. When two metals are mixed in the liquid state to produce a solution, the resulting alloy is called a binary alloy. The article describes the various types of solid solutions such as interstitial solid solutions and substitutional solid solutions. Free energy is important because it determines whether or not a phase transformation is thermodynamically possible. The article discusses the thermodynamics of phase transformations and free energy, as well as kinetics of phase transformations. It concludes with a description of solid-state phase transformations that occur when one or more parent phases, usually on cooling, produces a phase or phases.