Metal , generally alloying

Owing to its material properties - very light and very strong - beryllium is an important industrial metal. Generally alloyed with other metals such as copper, it is a key component of materials used in the aerospace and electronics industries. In addition, beryllium has a small neutron cross-section, which makes it useful in the production of nuclear weapons and in sealed neutron sources (Taylor et al. 2003). Unfortunately, beryllium is responsible for a severe lung disease, chronic beryllium disease (CBD) or berylliosis and, in addition, was listed in 1993 as a Class A human carcinogen by the International Agency for Research on Cancer (1993). 

Aqueous Corrosion. Several studies have demonstrated that ion implantation may be used to modify either the local or generalized aqueous corrosion behavior of metals and alloys (119,121). In these early studies metallic systems have been doped with suitable elements in order to systematically modify the nature and rate of the anodic and/or cathodic half-ceU reactions which control the rate of corrosion. 

The New York Commodity Exchange (Comex) prices for cathode copper in January 1993, 1994, and 1994 were 2.218/kg, 1.844/kg, and 3.084/kg, respectively. The primary uses for copper metal and alloy are constmction, 42% electrical/electronic, 24% industrial machinery, 13% transportation equipment, 11% and consumer/general products, 10%. Copper compounds for use in agriculture and industry account for about 1% of total copper consumption. 

Electroplated materials are generally employed for a specific property or function. There is, of course, some ovedap for example, decorative use certainly requires some degree of corrosion resistance. The various usages and the principal plating metals employed are as hsted. There are also smaller amounts of other metals and alloys used for specific apphcations. 

Structural Properties at Low Temperatures It is most convenient to classify metals by their lattice symmetiy for low temperature mechanical properties considerations. The face-centered-cubic (fee) metals and their alloys are most often used in the construc tion of cryogenic equipment. Al, Cu Ni, their alloys, and the austenitic stainless steels of the 18-8 type are fee and do not exhibit an impact duc tile-to-brittle transition at low temperatures. As a general nile, the mechanical properties of these metals with the exception of 2024-T4 aluminum, improve as the temperature is reduced. Since annealing of these metals and alloys can affect both the ultimate and yield strengths, care must be exercised under these conditions. 

The hexagonal-close-packed (hep) metals generally exhibit mechanical properties intermediate between those of the fee and bcc metals. For example Zn encounters a ductile-to-brittle transition whereas Zr and pure Ti do not. The latter and their alloys with a hep structure remain reasonably ductile at low temperatures and have been used for many applications where weight reduction and reduced heat leakage through the material have been important. However, small impurities of O, N, H, and C can have a detrimental effect on the low temperature ductihty properties of Ti and its alloys. 

TABLE 28-2 General Corrosion Properties of Some Metals and Alloys ... 

The 10 volumes in the Series on characterization of particular materials classes include volumes on silicon processir, metals and alloys, catalytic materials, integrated circuit packaging, etc. Characterization is approached from the materials user s point of view. Thus, in general, the format is based on properties, processing steps, materials classification, etc., rather than on a technique. The emphasis of all volumes is on surfaces, interfaces, and thin films, but the emphasis varies depending on the relative importance of these areas for the materials class concerned. Appendixes in each volume reproduce the relevant one-page summaries from the Encyclopedia and provide longer summaries for any techniques referred to that are not covered in the Encyclopedia. 

M = Metal (Generally 304 SS. Other alloys available) P = Plastic (Wide selection) C = Ceramic... 

Nickel and nickel-rich alloys must be considered as having generally poor resistance to molten metals. Eldred has made a systematic investigation of the attack of liquid metals on solid metals and alloys, and his results for nickel, and nickel-chromium and nickel-copper alloys, are summarised in Table 7.35. These are for tests at up to 500 C and apart from potassium and sodium all the low-melting-point metals investigated produced moderate to severe attack on the nickel-rich materials. Furthermore, the values for many of the combinations given in the table indicate a marked tendency to preferential intergranular attack. 

The structure and composition of diffusion coatings depends of necessity on the metal or alloy from which the article is made. Thus, for example, it is not possible to speak of chromised coatings generally the material into which chromium is diffused must be specified. Some data on methods of application and properties of commercially chromised irons and steels are given in Table 12.4. 

In general, many metals and alloys (e.g. of Al, Ta and Mo) can be deposited on metallic and some non-metallic substrates. M may also be a metal compound having special useful properties (e.g. borides, nitrides, oxides, silicides and carbides), or even a non-metal such as Si (as in Ihrigising ). 

Rubber vulcanised-determination of adhesion to, and corrosion of, metals Corrosion of metals and alloys determination of dezincification resistance of brass Sulphur dioxide test with general condensation of moisture... 

Corrosion of metals and alloys stress corrosion testing. Part 1 General guidance on testing procedures... 

Metals and alloys removal of corrosion products from corrosion test specimens Metals and alloys atmospheric corrosion testing general requirements for held tests Corrosion of metals and alloys. Classification of corrosivity of atmospheres Corrosion of metals and alloys. Guiding values for the corrosivity categories of atmospheres... 

Concentrated hydrochloric acid will dissolve many metals (generally those situated above hydrogen in the electrochemical series), as well as many metallic oxides. Hot concentrated nitric acid dissolves most metals, but antimony, tin and tungsten are converted to slightly soluble acids thus providing a separation of these elements from other components of alloys. Hot concentrated sulphuric acid dissolves many substances and many organic materials are charred and then oxidised by this treatment. 

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