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Powder metallurgy
About: Powder metallurgy is a research topic. Over the lifetime, 19751 publications have been published within this topic receiving 238540 citations.
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TL;DR: In this paper, the basic science of sintering and hipping is summarized and contrasted, and the current state of understanding and modeling of hipping can be classified either as microscopic or macroscopic in their approach.
Abstract: Hot isostatic pressing (hipping) can be used for upgrading castings, densifying presintered components, consolidating powders, and interfacial bonding. It involves the simultaneous application of a high pressure and elevated temperature in a specially constructed vessel. The pressure is applied with a gas (usually inert) and, so, is isostatic. Under these conditions of heat and pressure, internal pores or defects within a solid body collapse and diffusion bond. Encapsulated powder and sintered components alike are densified to give improved mechanical properties and a reduction in the scatter band of properties. In this article, the basic science of sintering and hipping is summarized and contrasted. The current state of understanding and modeling of hipping is then reviewed. Models can be classified either as microscopic or macroscopic in their approach. In the microscopic approach, the various mechanisms of densification are analyzed in terms of a single particle and its surroundings. In the macroscopic approach, the compact is treated as a continuous medium. In hipping, although the pressure is isostatic, shrinkage is not generally isotropic, particularly if containment is used. However, the shrinkage can now be well predicted, provided that the material and container properties are accurately known.
536 citations
TL;DR: Porous Ti compacts for biomedical applications are successfully fabricated in the porosity range from 50 to 371 vol% by controlling sintering conditions and Ti powder sizes as discussed by the authors, where Young's modulus and bending strength at the porosa of around 30 vol% are found to be similar to those of human cortical bone.
519 citations
Book•
01 Jan 1970
TL;DR: In this paper, the authors present a detailed discussion of the main factors affecting the transition of the Alumina phase and their effect on the performance of the process. But they do not consider the effect of other factors, such as temperature, dehydration, and deformation of the phase.
Abstract: INTRODUCTION. NOMENCLATURE. PREPARATION OF ALUMINA PHASES. Bauxite. Preparation of Bayer Alumina. Wet Alkaline Processes. Wet Acid Processes. Furnace Processes. Carbothermic Processes. Electrolytic Processes. Amorphous and Gel Aluminas. Preparation of the Alumina Trihydroxides. Gibbsite. Bayerite. Nordstrandite, Bayerite II, Randomite. Preparation of the Alumina Monohydroxides. Boehmite. Disapore. Transition Aluminas. Dehydration Mechanism. Sequence of Transition. Phases Formed on Aluminum. Rehydration. Alpha Alumina. Preparation. Factors Affecting Alumina Transitions. Special Ceramic Aluminas. Beta and Zeta Aluminas. Suboxides and Gaseous Phases. STRUCTURE AND MINERALOGICAL PROPERTIES. Structure of the Alumina Phases. Pseudomorphosis. Surface Area of Alumina. Porosity. Sorptive Capacity. MECHANICAL PROPERTIES OF ALUMINA. General Considerations. Bending, Compressive, Tensile, and Torsional Strength. Impact Strength. Moduli of Elasticity (E), and Rigidity (G). Poisson's Ration (i). Creep Characteristics. Thermal Shock. Internal Friction. Fatigue. Hardness and Abrasiveness of Alumina THERMAL PROPERTIES. Thermophysical and Thermochemical Constants. Specific Heat. Thermal Expansion. Thermal Conductivity. Thermal Diffusivity SONIC EFFECTS IN ALUMINA. Velocity of Sound in Alumina. Ultrasonic Absorption. ELECTRICAL PROPERTIES OF ALUMINA. Introduction. Electrical Conductivity of Alumina. Dielectric Constant and Loss Factor of Alumina. Dielectric Strength MAGNETIC PROPERTIES OF ALUMINA. Magnet Susceptibility. Magnetic Resonance of Alumina. OPTICAL PROPERTIES OF ALUMINA. Refractive Index of Alumina. Transmission, Emissivity, and Absorption of Alumina. Phosphorescence, Fluorescence, and Thermoluminescence. Optical Spectra of Alumina. Color in Alumina. Chromia-Alumina System, Laser Applications RADIATION AND ALUMINA. CHEMICAL PROPERTIES OF ALUMINA. Wet Chemical Reactions of Sintered Alumina. Reaction of the Chemical Elements with Alumina. Slagging Effects. Ash Slags. Slags Containing Sulfates. Steel Furnace Slags. Glass Furnace Reactions. Calcium Aluminate Slags. Aluminum Slag Reactions. Miscellaneous Reactions COLLOIDAL PROPERTIES OF ALUMINA. Plasticity. Surface Charge and Zeta Potential of Alumina. Flocculation and Deflocculation Effects. Additives GRINDING CERAMIC ALUMINA. FORMING ALUMINA CERAMICS. Cold Forming of Alumina. Hot-Pressing. Miscellaneous Forming Methods SINTERING. Introduction. Sintering Atmospheres. Sintering Additives ALUMINA IN REFRACTORIES. General. High-Alumina Refractories. Fused Cast Alumina Refractories. Clay-Bonded Alumina Refractories, Mullite Refractories. Spinel, Cordierite, Alumina-Chromite. Refractory Equipment. Refractories for Aluminum and Other Nonferrous Uses. Lightweight Alumina Refractories. Binders for Alumina Refractories ALUMINA AS AN ABRASIVE MATERIAL. Introduction. Loose Grain Abrasive. Grinding Wheels. Ceramic Tools ELECTRICAL APPLICATIONS. Spark Plug Insulators. Electron Tube Elements, High-Frequency Insulation. Alumina Porcelain Insulation. Resistors and Semiconductors CEMENT. Calcium Aluminate Cement. Barium Aluminates ALUMINA IN GLASS. Introduction. Bottle Glass. Devitrified Glasses Containing Alumina. Boron Glasses. Lithium Glasses, Phosphate Glasses. Optical Glasses ALUMINA IN COATINGS. Introduction. Anodic Coatings on Aluminum. Glazes and Enamels. Flame-Sprayed Coatings. Painted, Cast, or Troweled Coatings. Electrolytic Coatings. Evaporated Coatings. Dip Coatings, Cementation Coatings. Coatings on Alumina and Other Ceramic Bases. Alumina Coatings for Electrical Insulation. Alumina Coatings by Sputtering ALUMINA IN CERMETS AND POWDER METALLURGY. Introduction. Chromium-Alumina Cermets. (Iron, Nickel, Cobalt)-Alumina Cermets. Aluminum-Alumina Alloys. Miscellaneous Cermets ALUMINA IN AIRBORNE CERAMICS. Introduction. Gas-Turbine Accessories. Radomes and Rocket Equipment. SEALS, METALLIZING, WELDING. FIBERS, WHISKERS, FILAMENTS. Introduction. Alumina Fibers. Glass Fibers MISCELLANEOUS CERAMIC APPLICATIONS OF ALUMINA. References.
489 citations
TL;DR: In this article, a transmission electron microscope (TEM) was used to examine the carbon nanotube reinforced aluminum (Al) composites produced by hot-press and hot-extrusion methods.
Abstract: Carbon nanotube reinforced aluminum (Al) composites were produced by hot-press and hot-extrusion methods. The interfacial structure between the carbon nanotube and Al was examined using a transmission electron microscope (TEM), and the mechanical properties were measured by a tensile test. TEM observations have shown that the nanotubes in the composites are not damaged during the composite preparation and that no reaction products at the nanotube/Al interface are visible after annealing for 24 h at 983 K. The strength of the composites is only slightly affected by the annealing time at 873 K, while that of the pure Al produced in a similar powder metallurgy process significantly decreases with time. These studies are considered to yield experimental information valuable for producing high performance composites.
475 citations
TL;DR: In this article, the effects of CNTs on the tribological properties of these composites were evaluated, and the results demonstrated that the Ni-P-CNT electroless composite coating exhibited higher wear resistance and lower friction coefficient than Ni−P-SiC and Ni-p-graphite composite coatings.
448 citations