Metal materials with metallic properties formed by alloying processes (smelting, mechanical alloying, sintering, vapor deposition, etc.) of two or more metal elements are called alloys. Some alloys are also made by adding other nonmetallic elements to one metal, so the alloy may contain only one metallic element. Any element can be used as an alloying element, but it is still metal that is added in large quantities. The most basic, independent substances that make up an alloy are called components. Alloys composed of two components are called binary alloys, alloys composed of three components are called ternary alloys, and alloys composed of more than three components are called multivariate alloys. Alloys in the solid state have some common properties. First, most alloys have melting points below the melting point of any of the constituent metals in their composition. Second, the hardness of an alloy is generally greater than the hardness of any metal in its composition. Third, the electrical and thermal conductivity of the alloy is lower than that of any constituent metal. Finally, the alloy is more resistant to corrosion.
Due to the advantages of rich sources, simple production and good performance, alloys are widely used in many fields such as aerospace, construction, biomedicine, and machinery manufacturing.
- Aerospace: Alloys are widely used in aerospace. Among them, the most widely used alloy is aluminum-lithium alloy. For example, the first generation of aluminum-lithium alloys was mainly used in the wings and tails of aircraft. The second-generation aluminum-lithium alloy has the advantages of low density and high elastic modulus, and can be used in the preparation of fighter aircraft bodies and some long-range missile warhead shells. The third generation aluminum-lithium alloy has large strength, good toughness, damage resistance, excellent fatigue resistance, low anisotropy; corrosion resistance; good thermal stability, and can be used to prepare rocket fuel tanks. The fourth-generation aluminum-lithium alloy has higher static strength and fracture toughness, and can be used in the preparation of passenger aircraft fuselage stringers, floor grilles, and upper wing stringers.
Figure 1. Shape memory alloys are used to fold wings
- Construction: Alloys are used in a wide range of construction applications. For example, aluminum alloys can be processed into various profiles such as doors, windows, and stairs due to their advantages such as low density, high strength, good plasticity, and strong corrosion resistance. Zinc aluminum alloy can be used to make smart door locks.
Figure 2. Aluminium windows
- Biomedicine: Compared with applications in other fields, alloys have fewer applications in the medical industry, but alloys are developing faster and faster in the biomedical field. For example, cobalt chromium alloys are often used as materials for porcelain teeth. Compared with porcelain teeth made of other non-alloy materials, cobalt-chromium alloy porcelain teeth can effectively improve the patient's dental restoration effect and dental aesthetics, and the probability of complications after treatment is lower. In addition, nickel alloys can be used to make joint prostheses to replace damaged joints.
- Other fields: In addition to the above fields, alloys have extremely important applications in many other fields. For example, in the field of machinery manufacturing, in addition to the production of automobiles, high-speed rail, and ships, alloys can also be used to make some high-precision instruments. In artificial intelligence, alloys can be used in the manufacture of housings for robots, computers, and mobile phones. In addition, in daily life, because some alloys have good electrical and thermal conductivity, they can be used in the manufacture of kitchen utensils and the like.
Alloys can often be divided into three types: mixture alloys, solid melt alloys, and metal intercalated alloys.
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