Most of the metals obtained on an industrial scale are used for the production of alloys. Alloys are an important structural material in industry, construction, machine and aircraft construction. The bulk of the smelted iron, titanium, magnesium, aluminum is used for these purposes. Metals have found wide application in many sectors of the national economy in many respects precisely because of their ability to form alloys by mixing molten metals and their subsequent solidification. A very valuable quality of alloys is that they have properties that none of the alloy components have. For example, a gold / copper alloy has significant hardness, although gold and copper are very soft metals. The most famous application of bismuth is in low-melting alloys based on it. Most often, Wood's alloy is used, the mass fraction of bismuth in which is 50%, lead - 25%, tin - 12.5% ​​and cadmium - 12.5%. This alloy melts at 69 ° C, although each of the starting metals has a significantly higher melting point (Bi 271 ° C, Pb - 327 ° C, Sn - 232 ° C, Cd - 321 ° C). Such alloys are used as low-melting solders for the manufacture of fuses for electrical equipment. Here are the composition of some of the widespread alloys. Cast iron is an alloy of iron with carbon (mass fraction more than 2%), containing small amounts of silicon, manganese, phosphorus, sulfur, etc. Compared with pure iron, it has increased hardness and high brittleness. Steel is an alloy of iron, in which the mass fraction of carbon does not exceed 2%, and also contains small amounts of manganese, silicon, sulfur, phosphorus and other impurities. The addition of tungsten, vanadium, chromium, nickel and other metals to steel gives it a number of very valuable properties (heat resistance, corrosion resistance, high hardness, etc.). Bronze is an alloy of copper with some other metals (tin, aluminum, lead, silicon, etc.). Brass is an alloy of copper and zinc (mass fraction up to 35%). Possesses high plasticity. Nichrome is an alloy of nickel, chromium, iron, manganese. It has high electrical resistance and high heat resistance. Duralumin is an alloy of aluminum with a small amount of magnesium and copper.