This article reviews some of the trends in superalloy development as they relate to U.S. strategic materials availability and the aerospace industry. It discusses the supply sources and availability of strategic materials and summarizes the status of U.S. resources and reserves. The article presents a list of several superalloys that have been used in gas turbine engines or that are emerging as replacements because of the promise of increased operating temperatures and higher efficiencies for the aircraft of the future. It concentrates on the objectives, results, and methodology of the NASA Conservation of Strategic Aerospace Materials (COSAM) program.

Computational fluid dynamics (CFD) is reserved for computationally intensive three-dimensional simulations of thermal fluids systems where non-linear momentum transport plays an important role. This article presents the governing equations of fluid dynamics and an introduction to the CFD techniques for their solution. It introduces discretization techniques that are used by finite-difference, finite-volume, finite-element, spectral, and some particle methods, and the associated concepts of numerical stability and accuracy. The article describes two approaches for grid generation with complex geometries. The approaches include use of unstructured grids and use of special differencing methods on structured grids. It discusses the four-step procedures of the CFD process, namely, geometry acquisition, grid generation and problem specification, flow solution, and post-processing and synthesis. The article provides information on the engineering applications of the engineering CFD. Issues and directions for the engineering CFD are also described.

Low-temperature carburization hardens the surface of austenitic stainless steels through the diffusion of interstitial carbon without the formation of carbides. This article provides an overview on austenitic stainless steels and low-temperature carburization. It reviews the competing technologies and commercial application of low-temperature carburization. The article discusses several processing parameters, including activation of the surface, proper surface preparation, selection and condition of the alloy to be carburized, treatment temperature, and carburizing atmosphere for successful low-temperature carburization of austenitic stainless steels and other chromium-containing alloys. It describes the performance properties of the low-temperature carburized layer: fatigue resistance, wear resistance, erosion resistance, and corrosion resistance.

Discontinuously reinforced aluminum (DRA) alloy metal-matrix composites (MMCs) represent an advanced aluminum materials concept whereby ceramic particles, or whiskers, are added to aluminum-base alloys through the use of either ingot-melting or casting and/or powder-metallurgy (P/M) techniques. This article begins with a summary of general observations on the forging of discontinuously reinforced composites. It provides information on some of the specific experimental results obtained on various DRA systems, including 2xxx DRA alloys and cast DRA alloys. The article reviews the efforts on the modeling of behavior of specific alloy systems, with a comparison of experimental results to the modeling attempts. It concludes with information on the properties of deformation-processed DRA alloys.

This article begins with a general review of the effects of changes in stress state on processing of materials. It describes the fundamentals of hydrostatic extrusion and reviews the various issues and benefits associated with hydrostatic extrusion. The article discusses the hydrostatic extrusion of structural alloys, composites, brittle materials, and intermetallics or intermetallic compounds, with examples. It concludes with a discussion on the attempts made to extend the hydrostatic extrusion to higher temperatures.

The biocompatibility of a material relates to its immunological response, toxicity profile, and ability to integrate with surrounding tissue without undesirable local or systemic effects on a patient. This article underscores the transformation of the medical device design ecosystem engaged as an integral part of the device ecosystem. It discusses the various applications of biomaterials, including orthopedic, cardiovascular, ophthalmic, and dental applications. The article describes the four major categories of biomaterials, such as metals, polymers, glass and ceramics, and composites. A discussion on natural materials, nanomaterials, and stem cells is also provided. The article concludes with information on examples of biomaterials applications, including endovascular devices, knee implants, and neurostimulation.

This article reviews the tensile properties and toughness characteristics of discontinuously reinforced aluminum (DRA) composites in terms of particle spacing, particle size, volume fraction, matrix alloy, and matrix microstructure. Both fracture toughness data and impact toughness data of the DRA composites are summarized. The article discusses the effects of confining pressure on the ductility of the DRA materials. It describes the fatigue behavior, such as stress-life behavior, strain-life behavior, and fatigue crack propagation, of the DRA.

This article first describes the two methods used in the 1998 U.S. corrosion cost study. In the first method, the cost was determined by summing the costs for corrosion control methods and contract services. In the second, the cost of corrosion was first determined for specific industry sectors and then extrapolated to calculate a national total corrosion cost. The article then reports the results and conclusions of the study. It concludes with information on corrosion prevention strategies.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of polymers, including polycarbonate, polyethylene, and polyimide, and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the quasi-brittle fatigue crack propagation, brittle and ductile fracture, crack-growth mechanisms, tearing, fibrillation, and fatigue striations of these surfaces.

Gallium-base components can be found in a variety of products ranging from compact disk players to advanced military electronic warfare systems, owing to the factor that it can emit light, has a greater resistance to radiation and operates at faster speeds and higher temperatures. This article discusses the uses of gallium in optoelectronic devices and integrated circuits and applications of gallium. The article discusses the properties and grades of gallium arsenide and also provides information on resources of gallium. The article talks about the recovery techniques, including recovery from bauxite, zinc ore and secondary recovery process and purification. The article briefly describes the fabrication process of gallium arsenide crystals. Furthermore, the article gives a short note on world supply and demand of gallium and concludes with research and development on gallium arsenide integrated circuits.

This article focuses on products defined by dimensions and tolerances and fabricated by some manufacturing process. It describes the general concepts associated with cost estimation. These include domain limitation, database commonality, cost allocation, and elements of cost. The article discusses the three methods of cost estimation, namely, parametric methods, empirical methods, and complexity theory. Examples of the methods of cost estimation are presented. The article concludes with a discussion on recommendations for cost estimation.

Product design greatly influences the recycling and reuse of manufacturing materials. This article presents a design for recycling strategy based on ease of disassembly, minimizing process scrap, using readily recyclable materials, and labelling or otherwise identifying parts. It also discusses the concept of life-cycle analysis (LCA), a quantitative accounting of the environmental and economic costs of using a given material and the energy required to make, distribute, operate, and eventually dispose of the host product and its constituent materials. An important but often overlooked step in the LCA process is to identify potential improvement pathways.

This article discusses the advantages, limitations, and applications of material jetting of ceramics, focusing on two primary methods of droplet formation: continuous stream and drop on demand (thermal and piezoelectric) ink jetting processes.

Germanium is a semiconducting metalloid element found in Group IV A. Germanium is used in the field of electronics, infrared optics, and in the fields of gamma ray spectroscopy, catalysis, and fiber optics. This article discusses the sources, manufacturing, and processing of germanium, and focuses on the chemical properties of various germanium compounds, including germanium halides, germanates, germanides, germanes, inorganic, and organogermanium compounds. It also tabulates the physical, thermal, electronic, and optical properties of germanium, and explains the economical aspects and specifications of germanium. The article describes the analytical and test methods of germanium, including gravimetric method, titrimetric method, and spectral method. It provides a short note on toxicology, and concludes with the uses of germanium in different fields.

The food-based approaches are considered important sustainable strategies for preventing iron deficiency. The success of a food fortification program depends on the choice of food vehicles and the choice of iron fortificants, that is, iron sources. This article discusses iron sources, namely, elemental irons and iron compounds, used as fortificants. Common elemental iron powders such as plain pure iron powders, and common iron compounds such as ferrous sulfate used in food fortifications, are reviewed. The article contains tables that list the food chemical codex requirements and the physical and chemical properties of commercial food-grade elemental irons.

Remarkable changes in information technology have occurred, and information and data are now routinely available by way of the World Wide Web. This article lists selected information sources and databases and demonstrates the way they are accessed. It presents information for a corrosionist in five areas: societies and associations addressing corrosion and related topics; corrosion standards, specifications, recommended practices, and related topics; sources of corrosion information; corrosion databases and data compilations; and other web resources.

Beryllium is a metal with an unusual combination of physical and mechanical properties that make it particularly effective in optical components, precision instruments, and specialized aerospace applications. Almost all of the beryllium in use is a powder metallurgy (P/M) product. Beginning with an overview of the mining and refining processes of beryllium, this article discusses powder production and consolidation methods, beryllium grades and their designations, and the protective measures that have been enacted to reduce exposure to beryllium.