Classification of alloys
Depending on the structure, the main types of alloys are:
(1) Mixed alloys (eutectic mixtures), which are formed when the components of the alloy crystallize separately when the liquid alloy solidifies, such as solder, bismuth-cadmium alloys, etc.
(2) Solid-solution alloys, alloys that form a solid solution when the liquid alloy solidifies, such as gold-silver alloys, etc.
(3) Intermetallic alloys, alloys in which the components form compounds with each other, such as brass (β -brass, γ -brass and ε -brass) composed of copper and zinc.
Many of the properties of alloys are superior to those of pure metals, so alloys are mostly used in application materials (see ferroalloys, stainless steel).
Characteristics of alloys
All types of alloys have the following characteristics:
(1) The melting point of most alloys is lower than that of any of the constituent metals;
(2) Hardness is generally greater than that of any of the metals in its composition; (Special case: sodium-potassium alloys are liquid and used as heat transfer agents in atomic reactors)
(3) The electrical and thermal conductivity of the alloy is lower than that of any of the constituent metals. Taking advantage of this property of the alloy, materials with high resistance and high thermal resistance can be made. Materials with special properties can also be made, such as a corrosion-resistant stainless steel made by adding 15% chromium and 9% nickel to iron, which is suitable for the chemical industry.
(4) Some have strong corrosion resistance (such as stainless steel)