This article describes the nitriding methods of titanium alloys such as plasma nitriding and gas nitriding. It focuses on the interaction of titanium alloys, interaction of titanium with nitrogen, and the interaction of titanium with oxygen, carbon, and hydrogen. The article provides information on the wear and fatigue properties and corrosion resistance of nitrided titanium alloys, as well as the effect of nitriding on the biocompatibility of titanium. It also compares plasma-nitrided titanium alloys with alloy steels. It concludes with a short discussion on the effect of nitriding on the surface properties of titanium and two-phase α + β alloys.

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.

This article introduces the fundamental concepts of chemical thermodynamics and chemical kinetics in describing presolidification phenomena. For metallurgical systems, the most important thermodynamic variables are enthalpy and Gibbs free energy. A qualitative demonstration of the interrelationship between phase diagrams and thermodynamics is presented. The article discusses processes that generally limit the rates of chemical processes. These include nucleation of the product phase and interphase mass transport. The article provides a discussion on the dissolution of alloy with melting point lower than bath temperature and dissolution of alloy that is solid at bath temperatures.

This article provides a summary of the concepts discussed in the articles under the Section “Fundamentals of Corrosion” in ASM Handbook, Volume 13A: Corrosion: Fundamentals, Testing, and Protection. In this section, the thermodynamic aspects of corrosion are descried first followed by a group of articles discussing the fundamentals of aqueous corrosion kinetics. The fundamentals of gaseous corrosion are addressed next. The fundamental electrochemical reactions of corrosion and their uses are finally described.

Principles of metallic corrosion play a fundamental role in developing industrial processes that employ corrosion for constructive purposes. This article examines the changes in kinetics that occur with differentially small potential changes around the equilibrium electrode potentials of two reversible electrodes, such as copper and silver electrodes, in an electrochemical system. It provides a schematic illustration of a reversible cell with copper and silver electrodes to determine a reversible cell potential between the electrodes. An electrode becomes irreversible when the electrode reactions are displaced from equilibrium and the electrode potential is no longer at the equilibrium potential. The article describes irreversible cell potential by using galvanic cells, electrolytic cells, and corrosion cells.

The electrode potential is one of the most important parameters in the thermodynamics and kinetics of corrosion. This article discusses the fundamentals of electrode potentials and illustrates the thermodynamics of chemical equilibria by using the hydrogen potential scale and the Nernst equation. It describes galvanic cell reactions and corrosion reactions in an aqueous solution in an electrochemical cell. The article explores the most common cathodic reactions encountered in metallic corrosion in aqueous systems. The reactions included are proton reduction, water reduction, reduction of dissolved oxygen, metal ion reduction, and metal deposition. The article also presents the standard equilibrium potentials measured at 25 deg C relative to a standard hydrogen electrode for various metal-ion electrodes in a tabular form.

This article provides a general introduction to the kinetics of aqueous corrosion with an emphasis on electrochemical principles. It describes the thermodynamic basis for corrosion by determining the equilibrium potentials of electrochemical reactions from the Nernst equation. A corrosion process can be controlled by the electronic conductivity of passive films when the cathodic reaction occurs on the surface of the film and by activation control of corrosion. Passivation becomes thermodynamically possible when the corrosion potential exceeds the potential corresponding to the equilibrium between a metal and one of its oxides/hydroxides. The article schematically illustrates a current-potential or polarization curve for an anodic process.

Corrosion of metallic materials is governed by electrochemical kinetics, so that the general concepts developed for studying electrochemical reaction mechanisms may be applied to corrosion. This article presents the fundamental aspects of electrode kinetics. The processes of charge transfer taking place at the electrode interface within the double layer and of mass transport at the vicinity of the electrode surface are discussed. The article describes the corrosion processes, which involve anodic and cathodic reactions at specific electrode sites. Some experimental methods for devising a reliable reaction model are detailed. The article explains some reaction mechanisms for cathodic and anodic processes to illustrate the great variety of reaction mechanisms occurring at the electrode interface.

This article describes the Schottky defect and the Frenkel defect in oxides. It provides information on the p-type metal-deficit oxides and n-type semiconductor oxides. The article discusses diffusion mechanisms and laws of diffusion proposed by Fick. It explains the oxide texture of amorphous and epitaxy oxide layers and presents equations for various oxidation reaction rates. The article reviews different theories to describe the oxidation mechanism. These include the Cabrera-Mott, Hauffe-IIschner, Grimley-Trapnell, Uhlig, and Wagner theories.

This article describes the vapor-phase growth techniques applied to the epitaxial deposition of semiconductor films and discusses the fundamental processes involved in metal-organic chemical vapor deposition (MOCVD). It reviews the thermodynamics that determine the driving force behind the overall growth process and the kinetics that define the rates at which the various processes occur. The article provides information on the reactor systems and hardware, MOCVD starting materials, engineering considerations that optimize growth, and the growth parameters for a variety of Group III-V, II-VI, and IV semiconductors.