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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
... 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...
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.a0005302
EISBN: 978-1-62708-187-0
... Abstract Grain refinement in aluminum casting alloys tends to reduce the amount of porosity and the size of the pores and to improve mechanical properties, especially fatigue strength. This article provides information on measurement of grain size in alloys and describes the mechanisms of grain...
Abstract
Grain refinement in aluminum casting alloys tends to reduce the amount of porosity and the size of the pores and to improve mechanical properties, especially fatigue strength. This article provides information on measurement of grain size in alloys and describes the mechanisms of grain refinement in aluminum casting alloys. It reviews the use of boron and titanium as a grain refiner for aluminum casting alloys. The article discusses the best practices for grain refinement in various aluminum casting alloys. These include aluminum-silicon casting alloys, aluminum-silicon-copper casting alloys, aluminum-silicon-copper casting alloys, aluminum-zinc-magnesium casting alloys, and aluminum-magnesium casting alloys. The article also discusses benefits of grain refinement in aluminum casting alloys.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0003995
EISBN: 978-1-62708-185-6
... schedules. The article describes the metallurgical processes in grain refinement of austenite steel by hot working, such as recovery and recrystallization and strain-induced transformation. The grain refinement in high strength low alloy steel by alloy addition is also discussed. The article provides an...
Abstract
Thermomechanical processing (TMP) refers to various metal forming processes that involve careful control of thermal and deformation conditions to achieve products with required shape specifications and good properties. This article describes TMP methods in producing hot-rolled steel and reviews how improvements in the strength and toughness depend on the synergistic effect of microalloy additions and on carefully controlled thermomechanical conditions. It discusses TMP variables and the general distinctions between conventional hot rolling and common types of controlled-rolling schedules. The article describes the metallurgical processes in grain refinement of austenite steel by hot working, such as recovery and recrystallization and strain-induced transformation. The grain refinement in high strength low alloy steel by alloy addition is also discussed. The article provides an outline on the key stages of deformation, and the required metallurgical information at each of these stages.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005247
EISBN: 978-1-62708-187-0
... castings (alloys with 12% Si or less) is, on the other hand, accomplished by chemically inhibiting the usual nucleation of eutectic silicon, causing eutectic aluminum grains to nucleate first and forcing silicon to then grow between those aluminum grains, thus acquiring a fibrous, broomlike morphology...
Abstract
Primary silicon in hypereutectic aluminum-silicon alloys is very hard, not only imparting improved wear resistance but also decreasing tool life during machining. This article discusses the importance of primary silicon refinement and the process of accomplishing primary silicon refinement.
Book Chapter
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005303
EISBN: 978-1-62708-187-0
..., deoxidation, grain refining, and filtration. The article provides a discussion on these melt treatments for group I to III alloys. It describes the three categories of furnaces for melting copper casting alloys: crucible furnaces, open-flame furnaces, and induction furnaces. The article explains the important...
Abstract
This article describes the casting characteristics and practices of copper and copper alloys. It discusses the melting and melt control of copper alloys, including various melt treatments to improve melt quality. These melt treatments include fluxing and metal refining, degassing, deoxidation, grain refining, and filtration. The article provides a discussion on these melt treatments for group I to III alloys. It describes the three categories of furnaces for melting copper casting alloys: crucible furnaces, open-flame furnaces, and induction furnaces. The article explains the important factors that influence the selection of a casting method. It also describes the production of copper alloy castings. The article concludes with a discussion on the gating and feeding systems used in production of copper alloy castings.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005331
EISBN: 978-1-62708-187-0
... stoichiometry of intermetallic phases, and control of solidification conditions. The article discusses the modification and grain refinement of aluminum-silicon alloys by the use of modifiers and refiners to influence eutectic and hypereutectic structures in aluminum-silicon alloys. It provides information on...
Abstract
This article begins with a discussion on the effects of alloying and impurity elements on the properties of aluminum cast alloys and their chemical compositions. It describes various means of structural control, namely, chemistry control, control of element ratios based on the stoichiometry of intermetallic phases, and control of solidification conditions. The article discusses the modification and grain refinement of aluminum-silicon alloys by the use of modifiers and refiners to influence eutectic and hypereutectic structures in aluminum-silicon alloys. It provides information on the foundry alloys for specific casting applications. The article concludes with a discussion on the heat treatment practices and properties of aluminum casting alloys.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0003993
EISBN: 978-1-62708-185-6
... Abstract This article provides a discussion on forging methods, melting procedures, forging equipment, forging practices, grain refinement, and critical factors considered in forging process. It describes the different types of solid-solution-strengthened and precipitation-strengthened...
Abstract
This article provides a discussion on forging methods, melting procedures, forging equipment, forging practices, grain refinement, and critical factors considered in forging process. It describes the different types of solid-solution-strengthened and precipitation-strengthened superalloys, namely, iron-nickel superalloys, nickel-base alloys, cobalt-base alloys, and powder alloys. The article discusses the microstructural mechanisms during hot deformation and presents processing maps for various superalloys. It concludes with a discussion on heat treatment of wrought heat-resistant alloy forgings.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004019
EISBN: 978-1-62708-185-6
... most, equal to 0.5. A typical example for isothermal grain growth in zone-refined iron is shown in Fig. 23 . The deviation from a straight-line relationship for very short annealing times at low temperatures is due to recrystallization, and that for long annealing times at high temperatures is due to...
Abstract
Recovery, recrystallization, and grain growth are microstructural changes that occur during annealing after cold plastic deformation and/or during hot working of metals. This article reviews the structure of the deformed state and describes the changes in the properties and microstructures of a cold-worked metal during recovery stage. It discusses the recrystallization that occurs by the nucleation and growth of grains. The article also reviews the growth behavior of the grains, explaining that the grain growth can be classified into two types: normal or continuous grain growth and abnormal or discontinuous grain growth. It also examines the key mechanisms that control microstructure evolution during hot working and subsequent heat treatment. These include dynamic recovery, dynamic recrystallization, metadynamic recrystallization, static recovery, static recrystallization, and grain growth.
Book Chapter
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004037
EISBN: 978-1-62708-185-6
... Abstract Control of grain flow is one of the major advantages of shaping metal parts by rolling, forging, or extrusion. This article shows the effects of anisotropy on mechanical properties. Cylindrical forgings commonly have a straight parting line located in a diametral plane. The alternate...
Abstract
Control of grain flow is one of the major advantages of shaping metal parts by rolling, forging, or extrusion. This article shows the effects of anisotropy on mechanical properties. Cylindrical forgings commonly have a straight parting line located in a diametral plane. The alternate classes of parting lines are called either "straight" or "broken" for brevity. Regardless of whether draft is applied or natural, the forging will have its maximum spread or girth at the parting line. Proper placement of the parting line ensures that the principal grain flow direction within the forging will be parallel to the principal direction of service loading. The article reviews the mutual dependence of parting line and forging process. It provides a checklist for the forging designer that suggests a systematic approach for establishing parting line location. Finally, the article contains examples, with illustrations of parting line locations, accompanied by tables of design parameters.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003248
EISBN: 978-1-62708-199-3
... fraction, grain structure (two-phase grain structures, and nonequiaxed grain structures), grain size, and inclusion content. It also reviews simple relationships between number of grains per unit area, number of intersections of a line of known length with particle or grain, and number of interceptions of...
Abstract
Quantifying microstructural parameters has received considerable attention and success in developing procedures and using such data to develop structure/property relationships has been achieved. This article reviews many of the simple stereological counting measurements of volume fraction, grain structure (two-phase grain structures, and nonequiaxed grain structures), grain size, and inclusion content. It also reviews simple relationships between number of grains per unit area, number of intersections of a line of known length with particle or grain, and number of interceptions of particles or grains by a line of known length.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0003999
EISBN: 978-1-62708-185-6
... Abstract Forging of nickel-base alloys results in geometries that reduce the amount of machining to obtain final component shapes and involves deformation processing to refine the grain structure of components or mill products. This article discusses the heating practice, die materials, and...
Abstract
Forging of nickel-base alloys results in geometries that reduce the amount of machining to obtain final component shapes and involves deformation processing to refine the grain structure of components or mill products. This article discusses the heating practice, die materials, and lubricants used in nickel-base alloys forging. It describes two major forging processing categories for nickel-base alloys: primary working and secondary working categories. Primary working involves the deformation processing and conversion of cast ingot or similar bulk material into a controlled microstructure mill product, such as billets or bars, and secondary working refers to further forging of mill product into final component configurations.
Book Chapter
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005306
EISBN: 978-1-62708-187-0
... composition but also through more precise control of microstructure. The absence of grain boundaries in single-crystal alloys permits elements such as carbon, zirconium, and boron to be deleted from the composition. The resulting increase in melting point in turn provides improved flexibility in alloy...
Book Chapter
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005199
EISBN: 978-1-62708-187-0
... ladles Properties are derived from the major refractory constituents, additives, microstructure, grain size, and fabrication process (bricks or castable). Changing these factors imparts specific characteristics that include melting temperature, creep resistance, oxidation resistance, corrosion...
Abstract
This article discusses the most common methods of melting steels, namely, electric arc and induction melting. It describes the classification of refractories by an index of the “basicity” of the slag formed on the steel surface. The steel melt refinements are classified as treatments by either converter metallurgy or ladle metallurgy. The article provides a detailed discussion on the converter and ladle metallurgy. The converter metallurgy includes melt refinement in argon oxygen decarburization (AOD) vessels and vacuum oxygen decarburization (VODC) in a converter vessel. The ladle metallurgy includes vacuum induction degassing, vacuum oxygen decarburization, and vacuum ladle degassing.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004020
EISBN: 978-1-62708-185-6
... in fine-grain metals has encompassed many ideas, such as the diffusional creep, dislocation creep with diffusional accommodation at grain boundaries, and concepts of grain-mantle deformation. The article concludes with information on the kinetics of superplastic deformation processes, including low...
Abstract
The constitutive relations for metalworking include elements of behavior at ambient temperature as well as high-temperature response. This article presents equations for strain hardening and strain-rate-sensitive flow, with alternate sections on empirically determined properties, followed by the models of constitutive behavior. It provides a discussion on creep mechanisms involving dislocation and diffusional flow, such as the Nabarro-Herring creep and the Coble creep. The equations for the several creep rates are also presented. Research on the mechanism of the superplastic flow in fine-grain metals has encompassed many ideas, such as the diffusional creep, dislocation creep with diffusional accommodation at grain boundaries, and concepts of grain-mantle deformation. The article concludes with information on the kinetics of superplastic deformation processes, including low stress behavior, concurrent grain growth, and high stress behavior.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003091
EISBN: 978-1-62708-199-3
..., and rotor steels have higher quality requirements and tighter composition control than plain carbon or ordinary low-alloy steels. The production of special-quality steels requires vacuum-based induction or electric remelting and refining capabilities. The article explores the types and characteristics...
Abstract
This article presents a detailed account on the process flow, composition, alternative sources, and the advancement of ironmaking, steelmaking and secondary steelmaking practices. Some steels, such as bearing steels, heat-resistant steels, ultrahigh strength missile and aircraft steels, and rotor steels have higher quality requirements and tighter composition control than plain carbon or ordinary low-alloy steels. The production of special-quality steels requires vacuum-based induction or electric remelting and refining capabilities. The article explores the types and characteristics of various steel manufacturing processes, such as ingot casting, continuous casting, and hot rolling. It provides an outline of specialized processing routes of producing ultralow plain carbon steels, interstitial-free steels, high strength low-alloy steels, ultrahigh strength steels, stainless steels, and cold-rolled products, and briefly explains the analytical techniques for liquid steels.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005204
EISBN: 978-1-62708-187-0
... Vacuum arc melting Electron beam melting Advantages Limitations Advantages Limitations Advantages Limitations Tungsten, molybdenum Small grain size; most often used Refining limited; small batches; high energy consumption Moderate grain size; acceptable workability; large ingots; low...
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005424
EISBN: 978-1-62708-196-2
... scale by modeling. At the crystal scale, issues often center around the influence of the polycrystalline microstructure on a material behavior. Simulations at this scale can combine morphological (size and shape) and topological (grain or phase connectivity) features with the anisotropy of both the...
Abstract
This article provides an explanation on how crystal plasticity is implemented within finite element formulations by the use of physical length scales: crystal scale and continuum scale. It provides theoretical formulations for kinematic framework for deforming crystals and polycrystals, elastic and plastic behaviors of single crystals, refinements to the single-crystal constitutive, and crystal-scale finite-element. The article also presents examples that illustrate the capabilities of the formulations at the length scales.
Book Chapter
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005202
EISBN: 978-1-62708-187-0
... the directed dendrites can come to a stop. The ingot core then solidifies nondirectionally, for example, in equiaxed grains, leading to segregation and microshrinkage. Even in the case of directional solidification, microsegregation increases with dendrite arm spacing. A solidification structure with...
Abstract
The vacuum arc remelting (VAR) process is widely used to improve the cleanliness and refine the structure of standard air melted or vacuum induction melted (VIM) ingots and also used in the triplex production of superalloys. This article illustrates the VAR process and the capabilities and variables of the VAR process. It also presents a discussion on the melt solidification, resulting structure, and ingot defects. The article concludes with a discussion on VAR process of superalloy, and titanium and titanium alloy.
Series: ASM Handbook
Volume: 4A
Publisher: ASM International
Published: 01 August 2013
DOI: 10.31399/asm.hb.v04a.a0005786
EISBN: 978-1-62708-165-8
... usually preferred to refine the final microstructure, enhancing strength and toughness. Due to grain growth or grain coarsening, the austenite grain size is expected to increase with time or temperature, as shown for pure iron in Fig. 12 . In alloys, the austenite grain-coarsening behavior may be...
Abstract
Austenitization refers to heating into the austenite phase field, during which the austenite structure is formed. This article highlights the purpose of austenitization, and reviews the mechanism and importance of thermodynamics and kinetics of austenite structure using an iron-carbon binary phase diagram. It also describes the effects of austenite grain size, and provides useful information on controlling the austenite grain size using the thermomechanical process.
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005403
EISBN: 978-1-62708-196-2
... size D 0 and the steady-state grain size D ¯ . If DDRX leads to grain refinement (more precisely, if D 0 ≥ 2 D ¯ ), the initial microstructure contains few nucleation sites (on the grain boundaries). The recrystallization process is associated with necklace formation until...
Abstract
Recrystallization is to a large extent responsible for their final mechanical properties. This article commences with a discussion on static recrystallization (SRX) and dynamic recrystallization (DRX). The DRX includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). The article discusses the assumptions and simplifications for the Avrami analysis. It describes the effects of nucleation and growth rates on recrystallization kinetics and recrystallized grain size based on the Johnson-Mehl-Avrami-Kolmogorov model for static recrystallization. The article reviews the kinetics of DRX with the aid of the Avrami relations. It considers the basic framework of the mesoscale approach for DDRX, including the three basic equations for grain size changes, strain hardening and dynamic recovery, and nucleation. The article explains the mesoscale approach for CDRX to predict microstructural evolutions occurring during hot deformation, along with an illustration of the main features of the CDRX mesoscale model.