Search Results for near-net shape manufacturing

Semisolid casting is a near-net shape manufacturing process capable of producing thick- and thin-walled complex-shaped components having excellent mechanical and functional performance. This article begins with a discussion on the history of semisolid processing and the advantages claimed for semisolid casting. It describes the four notable processes used to produce semisolid castings: thixocasting, rheocasting, thixomolding, and wrought processes. Most commercial aluminum semisolid casters use either thixocasting or rheocasting. The article discusses the die design, process conditions, and simulation for semisolid casting. It concludes with a review of several components produced by each of the various semisolid casting processes.

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 focuses on the use of electron beam (EB) for near-net shape processing based on the wire feed material-delivery method. EB deposition processes start with a 3-D model designed in a computer-aided design (CAD) environment, where the deposition path and process parameters are generated. The article provides a description of the electron beam direct manufacturing (EBDM) system used for manufacturing of target parts with the aid of a case study. The control of the essential variables of dynamic beam deflection is also reviewed. The article also includes information on the applications of high-frequency multibeam processes, namely, selective surface treatment, multiple-pool welding, and pre- and post-heat treating.

Additive manufacturing (AM) is a highly desired layer-by-layer fabrication process capable of creating near-net-shaped three-dimensional components for a wide range of industries, such as the automotive and aerospace industries. This article focuses on aluminum, titanium, and stainless steel alloys that are commonly used or highly desired for use with AM due to their widespread applicability and favorable mechanical properties. It presents an overview of two of the major AM processes: powder-bed and powder-fed. The article discusses processability using AM. It also provides an overview of material microstructures, defects, and the impact on mechanical behaviors.

Braiding is a textile process that is known for its simplicity and versatility. Braided structures are unique in their high level of conformability, torsional stability, and damage resistance. This article describes the braiding process and the mechanical properties of two-dimensional and three-dimensional braiding.

Prealloyed (PA) powder metallurgy is a technique where complex near-net shape titanium aircraft components are fabricated with low buy-to-fly ratios. This article describes the physical principle, mechanism, and simulation and modeling of metal can and hot isostatic pressing (HIP) processes involved in the PA powder metallurgy technique. It discusses the technical problems addressed in shape control and their solutions for understanding the advantages of powder metallurgy HIP.

Braided structures are unique in their high level of conformability, torsional stability, and damage resistance. This article describes the classifications of braiding such as two-dimensional braiding and three-dimensional braiding. It presents the governing equations for computer-controlled braiding in a table. The article lists the applications of braided fabrics and composites. It discusses the formation, structure, and properties of two-dimensional braid composites and three-dimensional braid composites: the damage tolerance and the impact damage limitation.

Hot-die forging and isothermal forging are unique forging methods developed to forge materials that are difficult or impossible to forge by conventional means. This article presents a comparative study on hot-die forging and isothermal forging. It discusses forging parameters, process selection considerations, design guidelines, alloy types and selection, and the advantages and disadvantages of hot-die forging and isothermal forging. The article discusses the application of the finite-element analysis modeling to design.

Laser deposition involves the articulation of a laser beam and the introduction of material into the beam path to fuse the material onto a substrate or into a functional shape. It can be divided into two broad categories: cladding and near-net shape processing. This article provides a discussion on the material combinations, characteristics of laser cladding, and the comparison with arc cladding. It reviews the characteristics and applications of near-net shape processing and explains the process involved in powder bed methods and direct powder methods.

This article describes the unique aspects of cold isostatic pressing (CIP) in comparison with die compaction, for powder metallurgy parts. It details the components of CIP equipment, including pressure vessels, pressure generators, and tooling material. The article reviews the part shapes and their influence in determining tap density of the filled mold. It provides a discussion on process parameters, such as dwell time, depressurization rate, evaluation of green strength and density, and thermal processing, and illustrates a process flowchart for the production of CIP parts.

This article discusses the two major applications of hot isostatic pressing (HIP), such as healing of inherent internal defects in castings and welds, and consolidation of powder materials. It describes the design principles of the HIP tooling, as well as the problems associated with mathematical modeling of HIP. The article presents an example for the modeling process of the HIP. It reviews the numerical modeling and tooling design of a casing component demonstration.

This article describes two rapid tooling technologies, namely, direct rapid tooling and indirect rapid tooling, for forging-die applications. Commonly used direct rapid tooling technologies include selective laser sintering, three-dimensional printing, and laser-engineered net shape process. The indirect rapid tooling technologies include 3D Keltool process, hot isostatic pressing, rapid solidification process tooling, precision spray forming, and radially constricted consolidation process.

Consolidation of titanium powders at room temperature may be performed by low-cost conventional powder metallurgy processes. This article provides information on various consolidation methods, namely, die pressing, direct powder rolling, and cold isostatic pressing. It also describes the sintering of blended elemental powders, high-strength titanium alloys, and porous material as well as the sintering of titanium powders by microwave heating.

This article provides a basic introduction to the various aspects of full density powder metallurgy, including properties, applications, processing methods, and process parameters.

The combination of high strength-to-weight ratio, excellent mechanical properties, and corrosion resistance makes titanium the best material choice for many critical applications. This article begins with a description of the historical perspective of titanium casting technology. It discusses the types of molding methods, such as rammed graphite molding and lost-wax investment molding. The article provides information on the casting design, melting, postcasting, and pouring practices. It describes the microstructure and mechanical properties of Ti-6AI-4V alloy. The article examines the product applications of titanium alloy castings. The tensile properties, standard industry specifications, and chemical compositions of various titanium alloy castings are tabulated.

This article discusses metal powder processing via hot isostatic pressing (HIP) and HIP cladding when metal powders are being employed in the cladding process. It traces the history of the process and details the equipment, pressing cycle, and densification mechanisms for HIP. The article describes the available process routes for fabricating products using HIP and the steps involved in the production of a part via direct HIP of encapsulated gas-atomized spherical powder. It concludes with information on the microstructures of 316L stainless steel HIP powder metallurgy valve body and a list of the mechanical properties of several powder metallurgy alloys.

This article reviews the general aspects of product design and provides an overview of the manufacturing processes and their relationship to design, with an emphasis on deformation processes. It discusses the various classes of deformation processes to illustrate their impacts on product design while taking advantage of the benefits of deformation processing.

This article explains the key features of the manufacturing techniques for polymer composites. It describes the selection of a technically and economically feasible manufacturing technique for a composite design. The article discusses widely accepted and emerging techniques to manufacture polymer composites such as open-mold techniques.

Precision forging is defined as a closed-die forging process in which the accuracy of the shape, dimensional tolerances, and surface finish exceed normal expectations to the extent that some of the postforge operations can be eliminated. This article provides an overview of the key factors that impact the precision forging process. It provides information on the achievable tolerances and presents examples of precision forging. A discussion on forging of bevel gears/spiral bevel gears is also presented.

Metal-matrix composites (MMCs) are a class of materials with potential for a wide variety of structural and thermal management applications. They are nonflammable, do not outgas in a vacuum, and suffer minimal attack by organic fluids, such as fuels and solvents. This article presents an overview of the status of MMCs, and provides information on physical and mechanical properties, processing methods, distinctive features, and various types of continuously and discontinuously reinforced aluminum, magnesium, titanium, copper, superalloy, and intermetallic-matrix composites. It further discusses the property prediction and processing methods for MMCs.