Technology & Engineering
Phase Transformations
Phase transformations refer to the changes in the structure of a material as it transitions from one phase to another, such as from solid to liquid or from one crystal structure to another. These transformations can significantly impact the mechanical, thermal, and electrical properties of materials, making them a crucial consideration in the design and processing of engineering materials.
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6 Key excerpts on "Phase Transformations"
eBook - PDF- Brent Fultz(Author)
- 2014(Publication Date)
- Cambridge University Press(Publisher)
PART III TYPES OF Phase Transformations Part III describes the important and established families of phase transitions in materials. Chapters 10–16 describe structural and chemical phase trans- formations of materials that occur by movements of atoms. These include heterogeneous first-order transitions such as melting and precipitation, and spinodal decomposition and ordering that may occur homogeneously as second-order phase transitions. Martensite and other displacive phase transi- tions are the subject of Chapter 15, and microstructural and nanostructural aspects of Phase Transformations are covered in Chapter 16. All these phase transitions involving atom rearrangements are historical figures in the field of materials science, and new phenomena are often explained with reference to them. Chapter 17 describes some of the major phase transitions involving elec- trons and spins that occur inside materials. Electronic and magnetic phase transitions can sometimes be understood with similar approaches as Phase Transformations involving atom rearrangements, but some aspects of electronic or magnetic excitations are not classical. This is emphasized in Chapter 18, which ends by touching on quantum criticality. Research on quantum phenom- ena such as superconductivity is often reliant on controlling the structures of materials. Likewise, results from condensed matter physics offer new insights into Phase Transformations in materials. 10 Melting The free energy of melting was discussed in Sect. 1.3.1. Thermodynamic equilibrium between the solid phase and the liquid phase was the starting point for the discussion on alloy freezing in Chapter 5, and of course the equilibrium thermodynamics are the same for either melting or freezing.
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
• 327 C h a p t e r 10 Phase Transformations: Development of Microstructure and Alteration of Mechanical Properties Two pressure–temperature phase diagrams are shown: for H 2 O (top) and CO 2 (bot- tom). Phase Transformations occur when phase boundaries (the red curves) on these plots are crossed as temperature and/or pressure is changed. For example, ice melts (transforms to liquid water) upon heating, which corresponds to crossing the solid–liquid phase boundary, as rep- resented by the arrow on the H 2 O phase diagram. Similarly, upon passing across the solid–gas phase boundary of the CO 2 phase diagram, dry ice (solid CO 2 ) sublimes (transforms into gaseous CO 2 ). Again, an arrow delineates this phase transformation. Liquid (Water) Pressure Pressure Vapor (Steam) Solid (Ice) Solid Liquid Gas Temperature Temperature SuperStock Charles D. Winters/Photo Researchers, Inc. WHY STUDY Phase Transformations? One reason metallic materials are so versatile is that their mechanical properties (strength, hardness, ductility, etc.) are subject to control and management over relatively large ranges. Three strengthening mechanisms were discussed in Chapter 7—namely grain size refinement, solid-solution strengthening, and strain hardening. Additional techniques are available in which the mechanical behavior of a metal alloy is influenced by its microstructure. The development of microstructure in both single- and two-phase alloys typically involves some type of phase transformation—an alteration in the number and/or char- acter of the phases. The first portion of this chapter is devoted to a brief discussion of some of the basic principles relating to transformations involving solid phases. Because most Phase Transformations do not occur instantaneously, consideration is given to the dependence of reaction progress on time, or the transformation rate. This is followed by a discussion of the development of two-phase microstructures for iron–carbon alloys.
eBook - PDF- Brent Fultz(Author)
- 2020(Publication Date)
- Cambridge University Press(Publisher)
PART III TYPES OF Phase Transformations Part III describes the important and established families of phase transitions in materials. Chapters 11–20 describe structural and chemical Phase Transformations of materials that occur by movements of atoms. These include heterogeneous first-order transitions such as melting and precipitation, and spinodal decomposition or ordering that may occur homogeneously as second-order phase transitions. Interfaces between phases are given special attention, since interfaces are where much of the dynamical change occurs, and intrinsic properties of interfaces are discussed in Chapter 11. Martensite and other displacive Phase Transformations are the subject of Chapter 19, and microstructural and nanostructural aspects of Phase Transformations are covered in Chapter 20. All these phase transitions involving atom rearrangements are historical figures in the field of materials science, and new phenomena are often explained with reference to them. Chapter 21 describes some of the major phase transitions involving electrons and spins. Electronic and magnetic phase transitions in materials can sometimes be understood with similar approaches as Phase Transformations involving atom rearrangements, although some aspects of electronic or magnetic excitations are not classical. 287 11 Thermodynamics and Phase Transitions at Surfaces Up to this point in the book, we have considered only bulk materials, nominally infinitely large, so there has been no role for a surface surrounding the material. Such an approach can explain much about phase transitions between two different crystal structures, for example, even when the materials are of micrometer dimensions. At nanometer dimensions, the situation is altered considerably by the high surface-to-volume ratio of the material, and this is a topic of Chapter 20.
eBook - PDFMaterials Science and Engineering
An Introduction
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
• 303 C h a p t e r 10 Phase Transformations: Development of Microstructure and Alteration of Mechanical Properties Two pressure–temperature phase diagrams are shown: for H 2 O (top) and CO 2 (bot- tom). Phase Transformations occur when phase boundaries (the red curves) on these plots are crossed as temperature and/or pressure is changed. For example, ice melts (transforms to liquid water) upon heating, which corresponds to crossing the solid–liquid phase boundary, as rep- resented by the arrow on the H 2 O phase diagram. Similarly, upon passing across the solid–gas phase boundary of the CO 2 phase diagram, dry ice (solid CO 2 ) sublimes (transforms into gaseous CO 2 ). Again, an arrow delineates this phase transformation. Liquid (Water) Pressure Pressure Vapor (Steam) Solid (Ice) Solid Liquid Gas Temperature Temperature Charles D. Winters/Photo Researchers, Inc. SuperStock WHY STUDY Phase Transformations? One reason metallic materials are so versatile is that their mechanical properties (strength, hardness, ductility, etc.) are subject to control and management over relatively large ranges. Three strengthening mechanisms were discussed in Chapter 7—namely grain size refinement, solid-solution strengthening, and strain hardening. Additional techniques are available in which the mechanical behavior of a metal alloy is influenced by its microstructure. The development of microstructure in both single- and two-phase alloys typically involves some type of phase transformation—an alteration in the number and/or char- acter of the phases. The first portion of this chapter is devoted to a brief discussion of some of the basic principles relating to transformations involving solid phases. Because most Phase Transformations do not occur instantaneously, consideration is given to the dependence of reaction progress on time, or the transformation rate. This is followed by a discussion of the development of two-phase microstructures for iron–carbon alloys.
eBook - ePubPhase Transformations
Examples from Titanium and Zirconium Alloys
- Srikumar Banerjee, Pradip Mukhopadhyay(Authors)
- 2010(Publication Date)
- Elsevier Science(Publisher)
Phase Transformations also occur in organic materials such as polymers, biological systems and liquid crystals. Many of the relevant concepts developed for inorganic systems have parallels in organic systems. However, no attempt will be made in this chapter to compare and contrast Phase Transformations in organic and inorganic systems as the nature of atomic interactions responsible for the transformations is quite different in these two classes of materials. Alloys, intermetallics and ceramics form a group of materials in which Phase Transformations can be discussed on a common conceptual basis and, therefore, a single classification scheme can be used for appropriately grouping different types of transformations in these systems. As mentioned earlier, Ti- and Zr-based systems, which include alloys, intermetallics and ceramics, exhibit nearly all possible types of Phase Transformations and, therefore, serve as excellent examples for studies on Phase Transformations in inorganic materials in general.Phase Transformations can be classified on the basis of different criteria, namely, thermodynamic, kinetic and mechanistic (Christian 1965 , Roy 1973 , Rao and Rao 1978 ). A comparison of the characteristic features of different types of transformations is presented in this chapter with a view to providing a coarse-brush picture of these in a generalized manner. The chapters which follow will describe these transformations more elaborately, taking illustrative examples from Ti- and Zr-based systems.2.2 Basic Definitions
In order to resolve some of the confusion and controversy which are of a semantic nature a summary of some basic definitions is presented here.A phase
eBook - PDFFundamentals of Materials Science and Engineering
An Integrated Approach
- William D. Callister, Jr., David G. Rethwisch(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
507 Two pressure–temperature phase diagrams are shown: for H 2 O (top) and CO 2 (bottom). Phase Transformations occur when phase boundaries (the red curves) on these plots are crossed as temperature and/or pressure is changed. For example, ice melts (transforms to liquid water) upon heating, which corresponds to crossing the solid–liquid phase boundary, as represented by the arrow on the H 2 O phase diagram. Similarly, upon passing across the solid–gas phase boundary of the CO 2 phase diagram, dry ice (solid CO 2 ) sublimes (transforms into gaseous CO 2 ). Again, an arrow delineates this phase transformation. 12 Phase Transformations Liquid (Water) Pressure Pressure Vapor (Steam) Solid (Ice) Solid Liquid Gas Temperature Temperature Sebastian Duda/Shutterstock Charles D. Winters/Science Source 508 Chapter 12 Phase Transformations Mechanical and other properties of many materials depend on their microstructures, which are often produced as a result of Phase Transformations. In the first portion of this chapter we discuss the basic principles of Phase Transformations. Next, we address the role these transformations play in the development of microstructure for iron–carbon and other alloys and how the mechanical properties are affected by these microstructural changes. Finally, we treat crystallization, melting, and glass transition transformations in polymers. 12.1 | | INTRODUCTION WHY STUDY Phase Transformations? The development of a set of desirable mechani- cal characteristics for a material often results from a phase transformation that is wrought by a heat treatment. The time and temperature de- pendences of some Phase Transformations are conveniently represented on modified phase dia- grams. It is important to know how to use these diagrams in order to design a heat treatment for some alloy that will yield the desired room- temperature mechanical properties.
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