Alloying metals

These compounds are obtained by action of halogenated organic derivatives on lead alloys (magnesium or alkaline metal alloys). 

To define a steel, it would be necessary to know its chemical composition, its physicochemical constitution, its metallurgical state (aimealed, hammered) and other parameters (superficial and chemical processing,. ..). The set of structural characters of a metallic alloy is consequently function of the chemical composition, the elaboration processing, the thermal processing, the temperature, etc. 

An important application of the HMT is the test for ferrous inclusions in high pressure turbine disks made from a non-magnetic metal alloy. On principle, such ferrous inclusions can be introduced during the manufacturing process and, if present, they can be the origin of cracks in these most critical parts. Therefore such tests are stringent necessary. 

Intermetallic compounds with gallium are used as semiconductors. Indium is used to coat other metals to protect against corrosion, especially in engine bearings it is also a constituent of low-metal alloys used in safety sprinklers. The toxicity of thallium compounds has limited the use of the metal, but it does find use as a constituent of high-endurance alloys for bearings. 

Titanium is important as an alloying agent with aluminum, molybdenum, manganese, iron, and other metals. Alloys of titanium are principally used for aircraft and missiles where lightweight strength and ability to withstand extremes of temperature are important. 

The tables in this section contain values of the enthalpy and Gibbs energy of formation, entropy, and heat capacity at 298.15 K (25°C). No values are given in these tables for metal alloys or other solid solutions, for fused salts, or for substances of undefined chemical composition. 

As a final example, the determination of carbon in steels and other metal alloys can be determined by heating the sample. The carbon is converted to CO2, which is collected in an appropriate absorbent trap, providing a direct measure of the amount of C in the original sample. 

Metal acetylides Metal-air cells Metal alcoholates Metal alkoxides Metal alloys Metal amalgams... 

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

Metallic Glasses. Under highly speciali2ed conditions, the crystalline stmcture of some metals and alloys can be suppressed and they form glasses. These amorphous metals can be made from transition-metal alloys, eg, nickel—2irconium, or transition or noble metals ia combination with metalloid elements, eg, alloys of palladium and siUcon or alloys of iron, phosphoms, and carbon. 

A molten metal alloy would normally be expected to crystallize into one or several phases. To form an amorphous, ie, glassy metal alloy from the Hquid state means that the crystallization step must be avoided during solidification. This can be understood by considering a time—temperature—transformation (TTT) diagram (Eig. 2). Nucleating phases require an iacubation time to assemble atoms through a statistical process iato the correct crystal stmcture... 

F. E. Tuhotsky, Amorphous Metallic Alloys, Butterworths, London 1983, p. 360. 

Lead and its alloys are generally melted, handled, and refined in cast-iron, cast-steel, welded-steel, or spun-steel melting ketdes without fear of contamination by iron (qv). Normal melting procedures require no dux cover for lead. Special reactive metal alloys require special alloying elements, duxes, or covers to prevent dross formation and loss of the alloying elements. 

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