This article focuses on various vacuum heat treating processes for additively manufactured parts, namely annealing and stress relieving, solid-solution annealing, and solution treating and aging. It addresses several practical concerns involved in using vacuum heat treatment, including temperature measurement, unvented cavities, loose powder, and direct contact of metals in the high-temperature vacuum. The article provides a short discussion on sintering and evaporation of metals in vacuum furnaces.

Work or strain hardening is a natural consequence of most working and forming operations on aluminum and its alloys. This article describes the annealing practices of strain-hardened alloys. It lists the temper designations for strain-hardened alloys. The article discusses the annealing of worked structures in terms of recovery, recrystallization, and grain coarsening. It summarizes some of the annealing treatments used in conjunction with fabrication by metal working, including preheating, interannealing, self-annealing, stabilization, and stoving. The article concludes with information on the key process parameters affecting the final properties of aluminum alloys.

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.

Gray irons are a group of cast irons that form flake graphite during solidification, in contrast to the spheroidal graphite morphology of ductile irons. This article describes surface hardening of gray irons by flame and induction heating. It provides information on the classification of the gray irons in ASTM specification. The article presents examples that illustrate the use of stress relieving to eliminate distortion and cracking. It describes the three annealing treatments of gray iron: ferritizing annealing, medium (or full) annealing, and graphitizing annealing. The article discusses the parameters of the tensile strength and hardness of a normalized gray iron casting. These include combined carbon content, pearlite spacing, and graphite morphology. The article concludes with a discussion on the induction hardening of gray iron castings.

The high-alloyed white irons are primarily used for abrasion-resistant applications and are readily cast into the parts needed in machinery for crushing, grinding, and handling of abrasive materials. This article discusses three major groups of the high-alloy white cast irons: nickel-chromium white irons, chromium-molybdenum irons, and high-chromium white irons. Mechanical properties for three white irons representing each of these three general groups are presented as bar graphs. The article also describes the various heat treatments of a martensitic microstructure, including austenitization, quenching, tempering, annealing, and stress relieving.

Cast irons, like steels, are iron-carbon alloys but with higher carbon levels than steels to take advantage of eutectic solidification in the binary iron-carbon system. This article introduces the solid-state heat treatment of iron castings and describes the various processes of heat treatment of cast iron. It provides information on stress relieving, annealing, normalizing, through hardening, and surface hardening of these castings. The article discusses general considerations for the heat treatment of cast iron. Cast irons are occasionally nitrided for various applications with the aim of enhancing surface hardness and corrosion resistance of the products. The article describes molten salt bath cyaniding and ion nitriding of cast iron.

Ductile cast irons are heat treated primarily to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article discusses the most important heat treatments of ductile irons and their purposes. International standards of ductile iron provided by ASTM International, the International Organization for Standardization (ISO), and SAE International are presented in a table. The article explains basic structural differences between the ferritic, pearlitic, martensitic, and ausferritic classes. It presents recommended practices for annealing ductile iron castings for different alloy contents and for castings with and without eutectic carbides. The article discusses the induction surface hardening and remelt hardening of ductile iron. It concludes with information on the effect of heat treatment on fatigue strength of ductile iron.

This article describes the annealing behavior of precious metals, namely, gold, silver, platinum, palladium, iridium, rhodium, ruthenium, and osmium. It discusses the annealing practices and their effect on the basic properties of common precious metal alloys. The article presents the typical properties and compositions of silver-copper alloys and gold jewelry alloys such as colored gold alloys and white gold alloys.

This article provides a detailed discussion on the heat treatment processes for titanium and titanium alloys. These processes are age hardening, solution treatment, aging, and annealing. The article illustrates the characteristics of equilibrium phase diagrams that are important for understanding the heat treatment of titanium alloys. It explains the types of metastable phases encountered in titanium alloys. The article also provides information on the equilibrium phase relationships and properties of titanium alloys.

Heat treatment of depleted uranium (DU) alloys with 4.0 wt% or more molybdenum or equivalent is similar to that of dilute alloys. This article discusses the metallurgical characteristics and processing considerations of DU and its alloys, and describes the control of grain size and orientation using beta treatment. It lists the typical mechanical properties of DU as functions of the amount of cold work and hardness data of uranium rod, and describes the annealing of cold-worked DU. The article also describes the heat treatment of dilute alloys of DU, focusing on the three basic furnace designs used for heating or heat treating of unalloyed uranium: molten salt baths, inert-atmosphere furnaces, and vacuum furnaces. Finally, it presents procedures that are examples of heat treatment used to meet certain specifications of ultimate tensile strength, yield strength, and elongation.

Cast and wrought coppers can be strengthened by cold working. This article provides information on minor alloying elements, such as beryllium, silicon, nickel, tin, zinc, and chromium, used to strengthen copper. It details annealing and recrystallization and grain growth characteristics of copper. The article also discusses the tensile-stress-relaxation behavior of selected types of copper wires.

This article describes the heat treatment of wrought solid-solution and precipitation-hardening alloys with a focus on the major families of wrought nickel alloys. It also provides information on the heat treatment of some representative solid-solution alloys in the Monel (Ni-Cu), Inconel (Ni-Cr-Mo), Hastelloy (Ni-Mo-Cr), and Incoloy (Ni-Fe-Cr) families of alloys. The heat treatment processes for gamma prime nickel alloys, gamma prime nickel-iron superalloys, and gamma double-prime nickel-iron superalloys are also included. The article also provides information on age-hardenable alloys, and the effects of cold work on aging response and grain growth with examples.

This article briefly discusses the annealing practices for refractory metals such as tungsten, molybdenum, niobium, tantalum, and rhenium and their alloys. It also presents the applications and properties of these metals and their alloys.

Brasses are copper alloys with zinc as the principal alloying element. This article provides information on the chemical compositions and mechanical properties of the three types of brasses: alpha, duplex and beta. It briefly discusses the Unified Numbering System designations, compositions, and classifications of wrought brasses and cast brasses. The article provides a discussion on annealing, recrystallization, and grain growth of wrought brasses. Stress relief of wrought brasses, which is typically conducted below the annealing temperatures, is also briefly described.

The most widely accepted alloy and temper designation system for aluminum and its alloys is maintained by the Aluminum Association and recognized by the American National Standards Institute (ANSI) as the American National Standard Alloy and Temper Designation Systems for Aluminum (ANSI H35.1). This article provides a detailed discussion on the alloy and temper designation system for aluminum and its alloys. The Aluminum Association alloy designations are grouped as wrought and cast alloys. Lengthy tables provide information on alloying elements in wrought aluminum and aluminum alloys; nominal composition of aluminum alloy castings; typical mechanical properties of wrought and cast aluminum alloys in various temper conditions; and cross references to former and current cast aluminum alloy designations.

This article describes the changes in structure and properties that occur when cold worked metals and alloys are annealed. Recovery, recrystallization, and grain growth are the three stages of structural change that occur when cold-worked metal is annealed. The driving force and extent of structural or property changes may depend on alloy structure and the degree of prior work.

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.

This article provides information on nickel alloying elements, and the heat treatment processes of various nickel alloys for applications requiring corrosion resistance and/or high-temperature strength. These processes are homogenization, annealing, solution annealing, solution treating, stabilization treatment, age hardening, stress relieving, and stress equalizing. Discussion of furnaces, fixtures, and atmospheres is included. Nickel alloys used for the heat treatment processes include corrosion-resistant nickel alloys, heat-resistant nickel alloys, nickel-beryllium alloys, special-purpose alloys such as nitinol shape memory alloys, low-expansion alloys, electrical-resistance alloys and soft magnetic alloys. Finally, the article focuses on heat treatment modeling for selecting the appropriate heat treatment process.

This article provides information on the Unified Numbering System designations and temper designations of copper and copper alloys. It discusses the basic types of heat treating processes of copper and copper alloys, namely, homogenizing, annealing, and stress relieving, and hardening treatments such as precipitation hardening, spinodal hardening, order hardening, and quench hardening and tempering. The article presents tables that list the compositions and mechanical properties of copper alloys. It also discusses two strengthening mechanisms of copper alloys, solid-solution strengthening and work hardening. Finally, the article provides information on the equipment used for the heat treating of copper and copper alloys, including batch-type atmosphere furnaces, continuous atmosphere furnaces, and salt baths.