Processing, aluminum alloys

P.R. Subramanian, N.V. Nirmalan, L.M. Young, P. Sudkamp, M. Larsen, P.L. Dupree, and A.K. Shukla, Effect of Microstructural Evolution in Mechanical and Corrosion Behavior of Friction Stir-Processed Aluminum Alloys, Friction Stir Welding and Processing II, K.V. Jata, M.W. Mahoney, R.S. Mishra, S.L. Semi-... 

Processing of Powder Metallurgy Alloys. Powder metallurgy processed aluminum alloys suffer from three major microstructural problems that limit their full potential prior-particle boundaries with an aluminum oxide film, microstructural inhomogeneity, and remnant porosity. These microstructural features particularly hamper the ductility in very high-strength aluminum alloys. Berbon et al. (Ref 59, 134)... 

M. Mahoney, C. Puller, M. Miles, and W. Bingel, Thick Plate Bending of Friction Stir Processed Aluminum Alloys, Friction Stir Welding and Processing III,... 

Aluminum. The majority of aluminum containers are of monobloc (one-piece) constmction, impact extmded from a slug of lubricated aluminum alloy. These containers are widely used for many products and are available in a vast array of heights and diameters. Because these containers lend themselves to additional shaping, many unusual shapes can be found in the marketplace. They may also be coated after the extmsion process. 

Molten cryohte dissolves many salts and oxides, forming solutions of melting point lower than the components. Figure 1 combines the melting point diagrams for cryolite—A1F. and for cryohte—NaF. Cryohte systems ate of great importance in the HaH-Heroult electrolysis process for the manufacture of aluminum (see Aluminumand ALUMINUM alloys). Table 5 Hsts the additional examples of cryohte as a component in minimum melting compositions. 

Uses. Alkah metal and ammonium fluoroborates are used mainly for the high temperature fluxing action required by the metals processing industries (see Metal surface treatments Welding). The tendency toward BF dissociation at elevated temperatures inhibits oxidation in magnesium casting and aluminum alloy heat treatment. 

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Eurther progress was made in the eighteenth and early nineteenth centuries. Many metals were discovered upon the development of experimental chemistry. The modem metallurgical industry was bom with the invention of steelmaking in 1856 (see Steel). Industrial processes for making zinc (see Zinc and zinc alloys), aluminum (see Aluminumand aluminum alloys), and copper followed before the end of the nineteenth century. These processes made possible the industrial revolution and the development of an industrial society relying heavily on the use of metals. 

Examples of similar processes are the decomposition of precipitated aluminum trHiydroxide to alumina, which is the feed for the electrolytic production of aluminum metal, and the drying of wet sulfide concentrates in preparation for flash roasting (see Aluminumand aluminum alloys). 

A.lkaline Solutions. The most important example of alkaline leach is the digestion of hydrated alumina from bauxite by a sodium hydroxide solution at 160-170°C, ie, the Bayer process (see Aluminumand aluminum alloys). 

The electrorefining of many metals can be carried out using molten salt electrolytes, but these processes are usually expensive and have found Httie commercial use in spite of possible technical advantages. The only appHcation on an industrial scale is the electrorefining of aluminum by the three-layer process. The density of the molten salt electrolyte is adjusted so that a pure molten aluminum cathode floats on the electrolyte, which in turn floats on the impure anode consisting of a molten copper—aluminum alloy. The process is used to manufacture high purity aluminum. 

Aluminum alloys are commercially available in a wide variety of cast forms and in wrought mill products produced by rolling, extmsion, drawing, or forging. The mill products may be further shaped by a variety of metal working and forming processes and assembled by conventional joining procedures into more complex components and stmctures. 

In bulk coating processes, bulk materials are joined to the substrate either by a surface melt process or by attachment of the soHd material. An example of the latter is the appHcation of heat-resistant tiles of sHica-type material to the aluminum alloy skin of a space shuttle vehicle, enabling the vehicle to withstand the reentry heat. 

Beryllium and aluminum are virtually insoluble in one another in the soHd state. The potential therefore exists for an aluminum—beryllium metal matrix composite with lower density and higher elastic modulus, ie, improved specific modulus, than conventional aluminum alloys produced by ingot or powder metal processing. At least one wrought composite system with nominally 62 wt % Be and 38 wt % A1 has seen limited use in aerospace appheations (see Composites). 

Refractories in the Aluminum Industry. Carbon materials are used in the HaH-Heroult primary aluminum cell as anodes, cathodes, and sidewalls because of the need to withstand the corrosive action of the molten fluorides used in the process (see Aluminumand aluminum alloys). 

Aluminum. Aluminum [7429-90-5] Al, is produced worldwide by the Bayer-HaH-Heroult process. This process involves the electrolysis of alumina [1344-28-1J, AI2O2, dissolved in molten cryoHte [15096-52-3] Na AIF (see Aluminumand aluminum alloys). The electrolytic cells or pots operate... 

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