Phase Transformations in Metals and Alloys

Citation

Porter, D. A., Easterling, K. E., & Sherif, M. Y. (2021). Phase Transformations in Metals and Alloys (4th ed.). CRC Press.

Chapter Summary

The fourth edition runs to about 578 pages in just six chapters, so each chapter is a long, self-contained treatment rather than a short unit. The order moves from the equilibrium and kinetic background (Chapters 1 to 3) to three families of transformation: solidification, diffusional transformations in the solid state, and diffusionless martensitic transformations (Chapters 4 to 6). According to the publisher, each chapter now closes with a summary of the main points.

Chapter 1: Thermodynamics and Phase Diagrams

The opening chapter supplies the thermodynamic language the later chapters use to say why a transformation happens and what it leads to. The publisher's list of changes in this edition places a new treatment of ternary phase diagrams and solubility products, and the concept of paraequilibrium in systems with highly mobile interstitial elements, in this territory. Everything after this chapter depends on reading phase diagrams as statements about driving force and equilibrium.

Chapter 2: Diffusion

Diffusion is treated as the second foundation, since most transformations in the book are limited by how fast atoms can move. The new edition adds the influence of segregation on grain boundary diffusion and points readers to software tools for solving diffusion problems in multicomponent systems.

Chapter 3: Crystal Interfaces and Microstructure

This chapter is about the boundaries and interfaces that shape microstructure. The fourth edition adds the thermodynamics of grain boundaries, an introduction to coincident site lattices and to methods for determining the dislocation content of grain boundaries and interfaces, and an updated treatment of coherency and interface structure, including the fcc-bcc interfaces that matter for steels.

Chapter 4: Solidification

The first of the three transformation chapters deals with the change from liquid to solid. The publisher notes that the treatment of metallic glasses has been expanded to cover the critical cooling rate, and lists the fir-tree structures seen in aluminum castings among the new practical applications.

Chapter 5: Diffusional Transformations in Solids

This chapter covers transformations in the solid state that proceed by atomic diffusion. Items on the publisher's list of revisions that belong here include the Austin-Rickett equation, introduced as an alternative to the Avrami equation for precipitation kinetics, a discussion of the effects of overlap in nucleation, growth and coarsening, and updated discussions of the pearlite and bainite transformations. The new practical applications attached to this territory include spinodal alloys and Al-Cu-Li aerospace alloys.

Chapter 6: Diffusionless Martensitic Transformations

The final chapter is described by the publisher as an entirely new and extensive treatment. It covers athermal and thermally activated martensite in ferrous systems and, for ordered nonferrous alloys, shape memory, superelasticity and rubber-like behavior. The new applications connected with it are quenched and partitioned steels, advanced high-strength steels, martensitic stainless steels, and superelastic and shape memory alloys.

Key Concepts

Chapters 1-3: Background

• Phase diagrams, including ternary diagrams: maps of which phases are stable under given conditions, extended in this edition to three-component systems.
• Paraequilibrium: a constrained equilibrium for systems in which interstitial elements move much faster than the substitutional ones.
• Multicomponent diffusion: diffusion in alloys with several solutes, for which the book refers readers to software tools.
• Grain boundary and interface structure: the thermodynamics of boundaries, coincident site lattices, dislocation content and coherency.

Chapters 4-6: Types of transformation

• Solidification and critical cooling rate: freezing of a liquid, and the cooling rate needed to form a metallic glass instead of a crystal.
• Precipitation kinetics: how the rate of a diffusional transformation is described, with the Austin-Rickett equation offered alongside the Avrami equation.
• Nucleation, growth and coarsening: the stages of a diffusional transformation and the effects of their overlap.
• Pearlite and bainite: the two diffusional transformations of steel whose discussion has been updated in this edition.
• Martensite: diffusionless transformation, covering athermal and thermally activated forms in steels and shape memory and superelastic behavior in nonferrous alloys.

Critical Analysis

Strengths

• Teaching-oriented design. The publisher describes a text based on the authors' teaching notes, with a pedagogical approach and examples and problems that can be used directly as exercises. Each chapter now ends with a summary of main points, which suits a book whose chapters are long.
• Theory linked to engineering alloys. The description stresses case studies of engineering alloys and a progression from basic theory to application. The new applications named (aluminum castings, aerospace Al-Cu-Li alloys, quenched and partitioned steels, advanced high-strength steels, martensitic stainless steels, shape memory alloys) show that the later chapters are tied to materials in current use.
• A substantially revised edition. According to the publisher, about 40 percent of the figures and 30 percent of the text are new, and the references and further reading have been updated for recent experimental and computational advances. A reader with an older edition therefore cannot assume the martensite material, in particular, is the same.
• Teaching support. A new solutions manual and PowerPoint figure slides are available to adopting instructors.

Limitations

• Few, very large chapters. Six chapters for roughly 578 pages means a single chapter may take weeks of a course. Readers who need only one topic, such as martensite, must still find their way through the background chapters it depends on.
• Metals and alloys only. The title and chapter list confine the book to metallic systems. Ceramics, polymers and glasses other than metallic glasses are not part of the plan.
• Modelling as context, not method. The publisher presents ab initio, phase field, cellular automaton and molecular dynamics methods as sources of insight woven into the text, and mentions software only for multicomponent diffusion. Students who want to learn to run such simulations will need other sources.
• Mixed entry level. The publisher describes a mix of basic and advanced information for students new to the field, yet topics such as ternary diagrams, paraequilibrium, coincident site lattices and the dislocation content of interfaces reach well beyond an introductory course. Readers should arrive with a first materials course behind them.

Where It Fits in the Course

Within this course list, the book is the specialist text on how microstructures form, and it is best read after a general introduction. Callister and Rethwisch's Materials Science and Engineering: An Introduction (listed in two editions) is a broad first course that connects atomic bonding and crystal structure with mechanical behavior and phase diagrams, which is the material Porter, Easterling and Sherif take for granted. Ashby, Shercliff and Cebon's design-led introduction starts from what engineers need materials to do, and Christopher Hall's Materials: A Very Short Introduction is a brief, non-technical orientation; both come before this book rather than alongside it.

Meyers and Chawla's Mechanical Behavior of Materials is the natural companion. It explains mechanical properties from the mechanisms operating at small scales, while Porter, Easterling and Sherif explain how the microstructures that those mechanisms act on are produced by heat treatment and processing. Reading the two together lets a student connect a processing route to the strength and toughness that result.

How to Use This Book

The book is meant for students of metallurgy and materials science and engineering who already know the basics of phase diagrams, crystal structures, thermodynamics and calculus. It suits a first graduate or final-year undergraduate course in physical metallurgy.

A practical plan:

• Core: Chapters 1 to 3 in order. Read Chapter 1 with the phase diagrams of familiar alloys beside it, and do not skip the interface chapter, because nucleation and growth in the later chapters are described in its terms.
• Choose by interest: Chapter 4 for casting, welding and glass formation; Chapter 5 for precipitation hardening, pearlite and bainite in steels and aluminum alloys; Chapter 6 for steels, shape memory and superelastic alloys. Chapters 5 and 6 are the ones most affected by the fourth edition's revisions.
• Exercises: work the end-of-chapter problems after reading each chapter summary, and treat the summary as a checklist of what the chapter should have taught you.
• Alongside: keep micrographs and a phase diagram handbook at hand, and use the book with a mechanical behavior text so that each transformation is linked to the properties it produces.