Structure-property relationships for metal additive manufacturing (AM) using solidification-based AM processes (e.g., powder-bed fusion and directed-energy deposition) are the focus of this article. Static strength and ductility properties in AM materials are impacted heavily by the microstructure but are also affected by porosity and surface roughness. Fatigue failure in AM materials is also influenced by porosity, surface roughness, microstructure, and residual stress due to applied manufacturing processing parameters. Post-processing treatments can further influence fatigue failure in AM materials.

This article focuses on characterizing the fracture-surface appearance at the microscale and contains some discussion on both crack nucleation and propagation mechanisms that cause the fracture appearance. It begins with a discussion on microscale models and mechanisms for deformation and fracture. Next, the mechanisms of void nucleation and void coalescence are briefly described. Macroscale and microscale appearances of ductile and brittle fracture are then discussed for various specimen geometries (smooth cylindrical and prismatic) and loading conditions (e.g., tension compression, bending, torsion). Finally, the factors influencing the appearance of a fracture surface and various imperfections or stress raisers are described, followed by a root-cause failure analysis case history to illustrate some of these fractography concepts.

Alloy 295.0 is an Al-Cu-Si alloy suitable for sand casting requiring high strength with ductility and toughness. This datasheet provides information on key alloy metallurgy, fabrication characteristics, processing effects on physical and mechanical properties, and applications of this series alloy. Room-temperature aging characteristics for aluminum alloy 295.0-F, -T4, -T6, and -T7 are also illustrated.

Aluminum wrought products, castings, welds, and fasteners are used in many structural applications where they are required to safely support a load. It is useful to design aluminum structural components with its structural properties in mind from conceptualization rather than attempting to mimic components of other materials. This article discusses design specifications, design requirements and methods, and material properties used in aluminum structural design. These properties include tensile yield strength and tensile ultimate strength, welding, and ductility. The article describes various factors that affect the strength of two categories of aluminum structural components, namely members and connections. Design requirements for aluminum bolts, rivets, screws, and pins are provided. The article concludes with a discussion on the considerations for serviceability, namely deflections and vibrations.

Alloys 7175 and 7475 are high-purity versions of 7075 to improve ductility in the transverse direction of thick products. This datasheet provides information on key alloy metallurgy and processing effects on physical and mechanical properties of these 7xxx series alloys. It also provides a fatigue life comparison of these alloys.

This article focuses on the tribological behavior of group 1, 2, and 3 cobalt-base alloys, namely, carbide-type wear-resistant alloys and laves-type wear-resistant alloys. The behavior includes hardness, yield strength and ductility, and fracture toughness. The article contains a table that lists the nominal compositions and typical applications of cobalt-base alloys. It discusses the properties and relative performance of specific alloys when subjected to the more common types of wear. These include abrasive wear, high-temperature sliding wear, rolling-contact fatigue wear, and erosive wear.

Malleable iron, like ductile iron, possesses considerable ductility and toughness because of its combination of nodular graphite and low-carbon metallic matrix. This article discusses melting practices such as batch cold melting and duplexing, and their control mechanisms. It schematically illustrates the microstructure of annealed ferritic malleable iron, which is characterized by microstructures consisting of uniformly dispersed fine particles of free carbon in a matrix of ferrite or tempered martensite. The article describes the digital solidification analysis technology, simulation technologies, and smart engineering for the production of malleable iron. It provides information on the applications of ferritic and pearlitic malleable irons.

Gray irons are commonly classified by their minimum tensile strength. This article describes properties used in the selection of gray irons and the factors that affect properties, particularly the effect of solidification. It discusses the three steps that its processing undergoes in the foundry: liquid metal preparation, solidification, and solid-state transformation. The article discusses the tensile properties of gray cast iron: tensile strength, yield strength, ductility, and modulus of elasticity. It describes hardness tests that are performed for determining the approximate strength characteristics and machinability of a gray iron casting. The article also presents typical mechanical properties of heat-resistant gray irons in a table. It concludes with information on the automotive application of alloy cast irons.

Malleable iron, like ductile iron, possesses considerable ductility and toughness because of its combination of nodular graphite and low-carbon metallic matrix. There are two basic types of malleable iron: blackheart and whiteheart. This article focuses on the blackheart malleable iron and discusses the chemical composition of malleable iron. A summary of mechanical properties and specifications of malleable iron castings is presented in a table. The article also reviews the mechanical properties of ferritic malleable iron and pearlitic and martensitic-pearlitic malleable irons.

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.

Milling of materials, whether hard and brittle or soft and ductile, is of prime interest and of economic importance to the powder metallurgy (PM) industry. This article discusses the principles of milling, milling parameters, and the powder characteristics required for the process. It discusses the changes in powder particle morphology that occur during milling of metal powders produced by various processes such as microforging, fracturing, agglomeration, and deagglomeration. The article also provides useful information on milling equipment such as tumbler ball mills, vibratory ball mills, attrition mills, and hammer and rod mills.

Air hardening steel is a type of steel that has deep hardenability and can be hardened in large sections by air cooling. This article discusses the principles of heat treatment of air-hardening steel, and describes the recommended heat treating practices for air-hardening high-strength structural steels, namely, H11 Mod, H13 steel, 300M steel, D-6A and D-6AC, and AF1410 steel. It also provides information on recommended heat treating practices for air-hardening martensitic stainless steels.

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.

This article focuses on the modeling and simulation of cavitation phenomena. It summarizes the experimental observations of cavitation and reviews the modeling of cavity nucleation and growth. The article discusses the modeling of the cavity growth based on mesoscale and microscale under uniaxial versus multiaxial tensile-stress conditions. Mesoscale models incorporate the influence of local microstructure and texture on cavitation. The article outlines the descriptions of cavity coalescence and shrinkage. It also describes the simulation of the tension test to predict tensile ductility and to construct failure-mechanism maps.

Homogenization, in a broad sense, refers to the processes designed to achieve uniform distribution of solutes or phases in a given matrix. This article addresses the root cause for inhomogeneities in cast components. It is nearly a standard industrial practice to homogenize alloys before thermomechanical processing. The article lists the objectives of homogenization and benefits of homogenization treatments. The benefits include increased resistance to pitting corrosion, increased resistance to stress-corrosion cracking, improved ductility, and uniform precipitate distribution during subsequent aging. The article provides a schematic illustration of an energy-dispersive X-ray spectroscope (EDS) scattered data of solute distributions across a dendrite due to microsegregation of chromium and molybdenum. It concludes with information on the computational modeling for simulation of microsegregation of chromium and molybdenum.

This article discusses two types of hot-tension tests, namely, the Gleeble test and conventional isothermal hot-tension test, as well as their equipment. It summarizes the data for hot ductility, strength, and hot-tension for commercial alloys. The article presents isothermal hot-tension test data, which helps to gain information on a number of material parameters and material coefficients. It details the effect of test conditions on flow behavior. The article briefly describes the detailed interpretation of data from the isothermal hot-tension test using numerical model. It also explains the cavitation mechanism and failure modes that occur during hot-tension testing.

This article describes the development of heat-resistant titanium-base alloys and their classification into several microstructure categories based on their strengthening mechanisms. It explains the phase transformation in titanium-aluminum-base alloys and two peritectic reactions that take place in the titanium-aluminum system. The article also describes two approaches for controlling the orientation of the high-temperature alpha phase to achieve the required lamellar orientation by directional solidification in order to improve the strength and ductility of titanium-aluminum alloys. One approach is by seeding the alpha phase in the alloys, and the other is without seeding, by controlling the solidification path of alloys through appropriate alloying. The article discusses the grain refinement technique used to improve the ductility of cast titanium-aluminum alloys to a level of above 1" at room temperature and reasonable room temperature ductility in the as-cast condition. Finally, it provides information on the microstructures produced through various near-net shape manufacturing processes.

This article provides a description of the microscale models and mechanisms for deformation and fracture. Macroscale and microscale appearances of ductile and brittle fracture are discussed for various specimen geometries and loading conditions. The article reviews the general geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography concepts.

Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.

Torsion tests can be carried out on most materials, using standard specimens, to determine mechanical properties such as modulus of elasticity in shear, yield shear strength, ultimate shear strength, modulus of rupture in shear, and ductility. This article discusses the torsional deformation of prismatic bars of circular cross-section and torsional response of prismatic bars of noncircular cross-section. It analyzes the elastic deformation, plastic deformation, and the effect of strain rate on plastic deformation. The article describes the theory of anisotropy in plastic torsion and the various components of a torsion testing machine. These include drive system, test section, torque and rotational displacement transducers, and rigid frame.