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temperature-dependent allotropic structure
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Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005441
EISBN: 978-1-62708-196-2
...Abstract Abstract This article presents a comprehensive collection of tables that list fundamental physical constants, standard atomic weights, melting points, atomic size parameters, heats of transition, thermal properties, temperature-dependent allotropic structures, pressure-dependent...
Abstract
This article presents a comprehensive collection of tables that list fundamental physical constants, standard atomic weights, melting points, atomic size parameters, heats of transition, thermal properties, temperature-dependent allotropic structures, pressure-dependent allotropic structures, and magnetic phase transition temperatures of the elements.
Book Chapter
Book: Alloy Phase Diagrams
Series: ASM Handbook
Volume: 3
Publisher: ASM International
Published: 27 April 2016
DOI: 10.31399/asm.hb.v03.a0006221
EISBN: 978-1-62708-163-4
... dependent on temperature and pressure; these materials are called polymorphic , or allotropic for pure elements. The most commonly used allotropic element is iron, which undergoes a series of phase transformations as a function of temperature and pressure ( Fig. 3 ). At room temperature, iron has...
Abstract
The application of phase diagrams is instrumental in solid-state transformations for the processing and heat treatment of alloys. A unary phase diagram plots the phase changes of one element as a function of temperature and pressure. This article discusses the unary system that can exist as a solid, liquid, and/or gas, depending on the specific combination of temperature and pressure. It describes the accomplishment of conversion between weight percentage and atomic percentage in a binary system by the use of formulas. The article analyzes the effects of alloying on melting/solidification and on solid-state transformations. It explains the construction of phase diagrams by the Gibbs phase rule and the Lever rule. The article also reviews the various types of alloy systems that involve solid-state transformations. It concludes with information on the sources of phase diagram.
Book Chapter
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003149
EISBN: 978-1-62708-199-3
... exhibit strong anisotropy because of two characteristics of the metal: zirconium has a hexagonal close-packed (hcp) crystal structure at room temperature, and it undergoes allotropic transformation to a body-centered cubic (bcc) structure at about 870 °C (1600 °F). The strong anisotropy profoundly...
Abstract
This article discusses the general characteristics, primary and secondary fabrication methods, product forms, and corrosion resistance of zirconium and hafnium. It describes the physical metallurgy of zirconium and its alloys, providing details on allotropic transformation and anisotropy that profoundly influences the engineering properties of zirconium and its alloys. Tables listing the values for chemical composition and tensile properties for nuclear and nonnuclear grades of zirconium are also provided.
Series: ASM Handbook
Volume: 2
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v02.a0001084
EISBN: 978-1-62708-162-7
... to a bcc structure at about 870 °C (1600 °F). Small amounts of impurities, particularly oxygen, strongly affect the transformation temperature ( Table 1 ). Variation in allotropic transformation temperature with oxygen content for unalloyed zirconium Table 1 Variation in allotropic transformation...
Abstract
Zirconium, hafnium, and titanium are produced from ore that generally is found in a heavy beach sand containing zircon, rutile, and ilmenite. This article discusses the processing methods of these metals, namely, liquid-liquid separation process, distillation separation process, refining, and melting. It also discusses the primary and secondary fabrication of zirconium and hafnium and its alloys. The article talks about the metallurgy of zirconium and its alloys with emphasis on allotropic transformation, cold work and recrystallization, anisotropy and preferred orientation, and the role of oxygen. It concludes by providing useful information on the applications of reactor and industrial grades of zirconium alloys.
Series: ASM Handbook
Volume: 18
Publisher: ASM International
Published: 31 December 2017
DOI: 10.31399/asm.hb.v18.a0006367
EISBN: 978-1-62708-192-4
..., if not specified otherwise. Allotropes of Carbon Different structural forms of carbon, which is one of the most flexible in bonding configurations among all materials, have found a niche in a wide range of applications. High thermal conductivity ( Ref 2 ) and tunable electrical properties ( Ref 3 , Ref 4...
Abstract
This article discusses the importance of friction and wear and the role of lubricants in composites. It highlights the progress and developments in using different forms of carbon allotropes in composites for improved friction and wear performance of materials. The article focuses on the widely used form known as carbon black (CB) and shows how to deal with friction and wear of polymers and composites when gamma irradiation is involved. It also discusses the role of graphite in composite materials, which is widely used as a dry lubricant. The article examines the tribology of carbon nanotubes (CNTs) as components in composite materials. It also highlights some of the most pronounced examples of graphene use as a reinforcement agent for improving tribological performance in composite matrices. The article concludes with a discussion on the progress of research in diamond-containing composites.
Book Chapter
Series: ASM Handbook
Volume: 4E
Publisher: ASM International
Published: 01 June 2016
DOI: 10.31399/asm.hb.v04e.a0006250
EISBN: 978-1-62708-169-6
..., the positions and orientations of the new grains depend on the deformed grain structure. Consequently, the recrystallization microstructure may be equivalent to the deformation microstructure but also may differ from it, depending on the temperature and time of the recrystallization anneal. Recrystallized...
Abstract
This article introduces the mechanism of diffusion and the common types of heat treatments such as annealing and precipitation hardening, which are applicable to most ferrous and nonferrous systems. Three distinct processes occur during annealing: recovery, recrystallization, and grain growth. The article also describes the various types of solid-state transformations such as isothermal transformation and athermal transformation, resulting from the heat treatment of nonferrous alloys. It provides information on the homogenization of chemical composition within a cast structure.
Series: ASM Handbook
Volume: 4E
Publisher: ASM International
Published: 01 June 2016
DOI: 10.31399/asm.hb.v04e.a0006286
EISBN: 978-1-62708-169-6
... symbol Definition α Low-temperature allotropic form of titanium with a hexagonal close-packed (hcp) structure; exists below β transus β High-temperature allotropic form with body-centered cubic (bcc) structure; exists at low temperature as metastable or stable phase in highly enriched alloys...
Abstract
Quenching is a widely used technique to strengthen titanium alloys. This article presents the metallurgical and structural background underlying the specific techniques applied in the quenching of various titanium alloys, and the ways to control and reduce residual stresses induced from quenching or other thermal or mechanical processes. It discusses the types and microstructures of titanium alloys, namely, alpha, alpha-beta, and beta alloys, and describes the general effects of the various heat treatments. The article provides information on quenching media, quenching rate, section size, and martensitic transformation in quenched titanium alloys. It shows how residual stresses in titanium alloys are evaluated and controlled. Finally, the article describes the stress-relief treatments used to reduce residual stresses.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003084
EISBN: 978-1-62708-199-3
... form, a phenomenon known as polymorphism. When found in elemental solids, the condition is known as allotropy. The prevailing crystal structure depends on both the temperature and external pressure. For example, at atmospheric pressure, iron is bcc at temperatures below 912 °C (1674 °F), fcc...
Abstract
Crystal structure is the arrangement of atoms or molecules in the solid state that involves consideration of defects, or abnormalities, in idealized atomic/molecular arrangements. The three-dimensional aggregation of unit cells in the crystal forms a space lattice or Bravais lattice. This article provides a brief review of the terms and basic concepts associated with crystal structures. It also discusses some of the significant defects obstructing plastic flow in real crystals, namely point defects, line defects, stacking faults, twins, and cold work. Several tables in the article provide information on the crystal structures and lattice parameters of allotropes of metallic elements.
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001430
EISBN: 978-1-62708-173-3
... potential sources of iron contamination be avoided. Steel wire brushes should not be used for interpass cleaning of titanium weldments. Titanium is a single (α) phase material with a hcp crystal structure. However, an allotropic transformation occurs at temperatures above approximately 870 °C (1600 °F...
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003085
EISBN: 978-1-62708-199-3
...”), depending on the conditions of state. State variables include composition, temperature, pressure, magnetic field, electrostatic field, gravitational field, and so forth. The term “phase” refers to that region of space occupied by a physically homogeneous material. However, there are two uses of the term...
Abstract
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.
Book Chapter
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003153
EISBN: 978-1-62708-199-3
..., small amounts of certain impurities, heat treatment, or plastic deformation. Several generally accepted structure-insensitive properties are the saturation induction ( B s ), resistivity (ρ), and Curie temperature ( T c ). These properties are largely dependent on the composition of the alloy selected...
Abstract
This article discusses the ferromagnetic properties of soft magnetic materials, explaining the effects of impurities, alloying elements, heat treatment, grain size, and grain orientation on soft magnetic materials. It describes the types of soft magnetic materials, which include high-purity iron, low-carbon irons, silicon (electrical) steels, nickel-iron alloys, iron-cobalt alloys, ferritic stainless steels, amorphous metals, and ferrites (ceramics). Finally, the article provides a short note on alloys for magnetic temperature compensation.
Book Chapter
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003116
EISBN: 978-1-62708-199-3
.... A wide range of forging temperatures can be used for most of the common austenitic types because of the natural workability of austenite and the absence of allotropic transformation. The conventional 18-8 types often are forged at temperatures up to 1260 °C (2300 °F). However, the upper temperature limit...
Abstract
Fabrication of wrought stainless steels requires use of greater power, more frequent repair or replacement of processing equipment, and application of procedures to minimize or correct surface contamination because of its greater strength, hardness, ductility, work hardenability and corrosion resistance. This article provides a detailed account of such difficulties encountered in the fabrication of wrought stainless steel by forming, forging, cold working, machining, heat treating, and joining processes. Stainless steels are subjected to various heat treatments such as annealing, hardening, and stress relieving. Stainless steels are commonly joined by welding, brazing, and soldering. The article lists the procedures and precautions that should be instituted during welding to ensure optimum corrosion resistance and mechanical properties in the completed assembly.
Series: ASM Handbook
Volume: 20
Publisher: ASM International
Published: 01 January 1997
DOI: 10.31399/asm.hb.v20.a0002460
EISBN: 978-1-62708-194-8
... defects. It discusses the relevance of the properties to design. The article describes the common means for increasing low-temperature strength and presents an example that shows structure-property relationships in nickel-base superalloys for high-temperature applications. The relationships...
Abstract
This article focuses on the relationships among material properties and material structure. It summarizes the fundamental characteristics of metals, ceramics, and polymers. The article provides information on the crystal structure, the atomic coordination, and crystalline defects. It discusses the relevance of the properties to design. The article describes the common means for increasing low-temperature strength and presents an example that shows structure-property relationships in nickel-base superalloys for high-temperature applications. The relationships of microstructure with low-temperature fracture, high-temperature fracture, and fatigue failure are also discussed.
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004000
EISBN: 978-1-62708-185-6
... criteria. Alpha-two titanium aluminides retain an ordered microstructure at temperatures close to 1100 °C (2010 °F), termed the critical ordering temperature, with the actual temperature dependent on aluminum content and other alloying elements employed. Current commercially significant alpha-two...
Abstract
Titanium alloys are forged into a variety of shapes and types of forgings, with a broad range of final part forging design criteria based on the intended end-product application. This article begins with a discussion on the classes of titanium alloys, their forgeability, and factors affecting forgeability. It describes the forging techniques, equipment, and common processing elements associated with titanium alloy forging. The processing elements include the preparation of forging stock, preheating of the stock, die heating, lubrication, forging process, trimming and repair, cleaning, heat treatment, and inspection. The article presents a discussion on titanium alloy precision forgings and concludes with information on the forging of advanced titanium materials and titanium aluminides.
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005401
EISBN: 978-1-62708-196-2
... of these topics is briefly discussed in this section. Phase Equilibria/Phase Transformations Microstructure and texture evolution and control in titanium alloys is heavily dependent on the allotropic transformation from the hcp crystal structure (denoted as alpha phase) found at low temperatures to a bcc...
Abstract
The modeling and simulation of texture evolution for titanium alloys is often tightly coupled to microstructure evolution. This article focuses on a number of problems for titanium alloys in which such coupling is critical in the development of quantitative models. It discusses the phase equilibria, crystallography, and deformation behavior of titanium and titanium alloys. The article describes the modeling and simulation of recrystallization and grain growth of single-phase beta and single-phase alpha titanium. The deformation- and transformation-texture evolution of two-phase (alpha/beta) titanium alloys are also discussed.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005337
EISBN: 978-1-62708-187-0
... temperature of the alloys. As a result, the cast dendritic β structure is wiped out during the solid-state cooling stage, leading to an α + β platelet structure ( Fig. 2 ), which is also typical of β-processed wrought alloy. Further, the convenient allotropic transformation temperature range of most titanium...
Abstract
The combination of high strength-to-weight ratio, excellent mechanical properties, and corrosion resistance makes titanium the best material choice for many critical applications. This article begins with a description of the historical perspective of titanium casting technology. It discusses the types of molding methods, such as rammed graphite molding and lost-wax investment molding. The article provides information on the casting design, melting, postcasting, and pouring practices. It describes the microstructure and mechanical properties of Ti-6AI-4V alloy. The article examines the product applications of titanium alloy castings. The tensile properties, standard industry specifications, and chemical compositions of various titanium alloy castings are tabulated.
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006309
EISBN: 978-1-62708-179-5
... during heat treatment. The final structure consists of graphite within a matrix of pearlite, pearlite and ferrite, or ferrite (depending on the cooling rate after annealing). The temper carbon is not truly spherical (as in ductile iron) but consists of irregularly shaped aggregates. Fig. 1 Forms...
Abstract
Malleable iron is a type of cast iron that has most of its carbon in the form of irregularly shaped graphite nodules instead of flakes, as in gray iron, or small graphite spherulites, as in ductile iron. This article discusses the production of malleable iron based on the metallurgical criteria: to produce solidified white iron throughout the section thickness; and to produce the desired graphite distribution (nodule count) upon annealing. It describes the induction heating and quenching or flame heating and quenching for surface hardening of fully pearlitic malleable iron. Laser and electron beam techniques also have been used for hardening selected areas on the surface of pearlitic and ferritic malleable iron castings that are free from decarburization.
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
... the melt. Nucleation-Controlled Peritectic Structures The classical description of peritectic reactions postulates heterogeneous nucleation of β at the α-liquid interface at the peritectic equilibrium temperature, T p . Undercoolings of up to 4% of T p are required for the systems investigated...
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.
Series: ASM Handbook
Volume: 4D
Publisher: ASM International
Published: 01 October 2014
DOI: 10.31399/asm.hb.v04d.a0005969
EISBN: 978-1-62708-168-9
... to produce temper carbon. When a white cast iron is heated for an extended period of time (up to about 60 h) at a temperature of 960 °C (1760 °F), the cementite decomposes into austenite and graphite. The final structure consists of graphite within a matrix of pearlite, pearlite and ferrite, or ferrite...
Abstract
This article focuses on heat treatment of malleable and compacted-graphite irons to produce ferritic and pearlitic malleable irons. It describes the heat treatment cycles of malleable iron, including martempering, tempering, bainitic heat treatment, and surface hardening. The article provides information on the mechanical and physical properties of compacted-graphite irons, which are determined by the graphite shape and the pearlite/ferrite ratio.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003086
EISBN: 978-1-62708-199-3
... it is frequently used, the term “property” connotes something that a material inherently possesses. More properly, a property should be regarded as the response of a material to a given set of imposed conditions (e.g., temperature and/or pressure). Material properties are the link between the basic structure...
Abstract
Material properties are the link between the basic structure and composition of the material and the service performance of a part or component. This article describes the most significant properties that must be considered when choosing a metal for a given application, namely physical properties (mass characteristics and thermal, electrical, magnetic, radiation, and optical properties), chemical properties (corrosion and oxidation resistance) and mechanical properties (tensile and yield strength, elongation, toughness, hardness, creep, and fatigue). The article also contains tables that list room-temperature physical properties, vapor pressures, and mechanical properties for various metals.