Metal alloys are liquid and solid systems.They are formed by alloying two or more elements.Connect and various metals.Initially, said term refers only to the material has metallic properties.However, due to the intensive development of engineering and physics definition greatly expanded and extended.
Metals and metal alloys are used widely in the production of designs of the equipment, machinery, tools and other things.Despite the relatively high prevalence creates an artificial product, the product of the above materials often form the basis of design, and experts predict that in the foreseeable future, will keep their positions.
alkaline earth and alkali metals (K, Na, Ca, Li) in a free state are used in nuclear reactors as a liquid metal.Sodium is used as a catalyst in the manufacture of rubber, lithium - doping a strong, lightweight aluminum compounds.They are used in aircraft.
metals (base metals) are found naturally in the salts, oxides and ores.Typically, in pure form in nature elements are chemically stable (Au, Pt, Cu, Ag).Among the open elements in the periodic system, seventy-six are metals, Si, Se, Ge, Te, As - to the intermediate elements between the non-metals and metals, they are sometimes called, and semimetals.
Metallic materials are classified into two large groups.The first is the iron and alloys (iron, steel), the second - non-ferrous metals and alloys non-ferrous metals.The latter, in turn, are divided into:
- light (density up to 5 g / cm3);
- heavy (density greater than 10 g / cm3);
- low melting (melting point from 232 to 410 degrees);
- refractory (melting point higher than that of iron);
- noble (having high corrosion resistance).
metals have different properties.For example, mercury freezes under the influence of temperature of minus 38.8 degrees, tungsten is able to withstand operating temperatures up to 2000 degrees, sodium, lithium, potassium, lighter than water, and osmium and iridium heavier lithium forty two times.Almost all the metal alloys have the characteristics of which are defined as the structure and composition of the compounds according to the conditions of cooling and solidification of mechanical and heat treatment.Cooling or heating help change the structure of the metal compounds.This in turn affects the physical, mechanical and chemical properties, the behavior of the material during processing and operation.
Experts identify the following general properties of metals and alloys:
- high thermal conductivity.
- increased ductility.
- high electrical conductivity.
- Positive Temperature indicator electrical resistance.This ratio indicates the increase in resistance with increasing temperature and at temperatures close to absolute zero - the superconductivity of many metallic materials.
- high reflectivity.Metallic materials are not transparent and have a characteristic metallic luster.
- thermionic emission - the ability to emit electrons when heated.
- in the solid state crystal structure.
to identify and verify the properties that the metal alloys, specialists use different control methods, including destructive.Thus, metallic materials tested for plasticity, strength, heat resistance, and resistance to corrosion.At the same time they apply non-destructive control methods.These include the measurement of magnetic, optical, and electrical properties, the determination of hardness.
