Is named alloy the process by which two or more elements, usually metallic, are combined in a single unit that gains the properties of both. For instance: steel, bronze, white gold, vital.
Alloys are usually considered homogeneous mixtures, since the atoms of the combined components do not produce (except in rare cases) chemical reactions that form a new chemical compound.
Normally, the substances used in alloys are metallic (iron, aluminum, copper, lead) but a metallic element can also be combined with a non-metallic element (carbon, sulfur, arsenic, phosphorus). It is important to clarify that at least one element must always be metallic for an alloy to form.
The resulting material of the mixture always has metallic characteristics (it shines, conducts heat and electricity, has more or less hardness, more or less malleability, more or less ductility), modified or strengthened with the addition of the other substance.
Types of alloys
A distinction is usually made between alloys based on the predominance of one element over others (for example, copper alloys). The base element It is the one that is in the greatest quantity in the alloy, while the alloy (s) are the ones that are found in the least quantity.
They are also classified according to the amount of elements involved in the mixture:
- Binary. They are made up of two elements (the base element and the alloying element).
- Ternary. They are made up of three elements (the base element and two alloys).
- Quaternary. They are made up of four elements (the base element and three alloys).
- Complex. They are made up of five or more elements (the base element and four or more alloys).
Another possible classification distinguishes between heavy and light alloys, according to the properties of the base metallic substance. For instance, aluminum alloys are light, but iron alloys are heavy.
Alloy properties
The specific properties of each alloy depend on the elements involved in the mixture, but also on the proportion that exists between them. The properties of an alloy are different from those of its individual elements.
By adding more alloying material, certain characteristics of the base material will be modified more, to the detriment of others. This proportion, depending on the alloy, can vary between minimum percentages (0.2 to 2%) or much more noticeable within the mixture.
Examples of alloys
- Steel. This alloy is essential for the construction industry since it is used to make beams or supports for pouring concrete or concrete. It is a resistant and malleable material, a product of the alloy of iron and carbon, mainly, although it can also contain silicon, sulfur and oxygen in even smaller proportions. The presence of carbon makes the iron more resistant to corrosion and more brittle at the same time, so in rare cases it exceeds a very small percentage. According to the presence of this last element, a whole range of usable steels is obtained.
- Brass. It is a material widely used in the container industry, especially those intended for non-perishable food, and in domestic plumbing and taps. Obtained from a copper-zinc alloy, it is highly ductile and malleable and shines easily when polished. According to the proportion between the elements, it is possible to obtain variants with various properties: more or less resistant to rust, more or less brittle, etc.
- Bronze. Bronze played a very important role in the history of mankind, as a material to make tools, weapons and ceremonial objects. Many bells were made with this material, as well as many coins, medals, national statues and various domestic implements, taking advantage of its enormous malleability and its economic obtaining from copper and tin.
- Stainless steel. This variant of ordinary steel (carbon steel) is prized for its extreme resistance to corrosion, making it ideal for making kitchen items, auto parts, and medical tools. To obtain this metal, chromium, nickel, molybdenum and tungsten are used in alloy with the steel.
- Amalgam. In frank disuse due to its mercury content that makes it slightly toxic to the human body, this metal filling used to be used as a dental sealant by dentists. It is the alloy of silver, tin, copper and mercury in a pasty substance that hardens when it dries.
- Duralumin. Duralumin is a light and resistant alloy that combines the properties of aluminum with those of magnesium, manganese, silicon and copper. It is used in the aeronautical industry and others that require a light, malleable and rust-resistant material.
- Pewter. Product of the alloy of copper, lead, tin and antimony, it is a substance long used in the elaboration of kitchen objects (cups, plates, pots, etc.) due to its extreme lightness and heat conduction. It is very malleable, a property that it receives from the unique elasticity of lead.
- White gold. Many jewels and ornamental objects are made from the so-called white gold: a very lustrous, brilliant and precious metal that is obtained by alloying gold, nickel, palladium or manganese. It is ideal for making jewelry that is lighter than pure gold, and it also allows you to use less of this precious metal, and achieve cheaper objects.
- Magnalium. It is an alloy highly demanded by the automotive and canning industries since, despite its low density, it has hardness, toughness and tensile strength. It is obtained by alloying aluminum with a magnesium content (barely 10%).
- Wood’s Metal. This alloy got its name from the dentist Barnabás Wood, its inventor, and is an alloy of 50% bismuth, 25% lead, 12.5% tin, and 12.5% cadmium. Despite its toxicity (due to the lead and cadmium it contains), it is used in melts and welds, and releases gases that should not be inhaled. Today, however, there are less toxic alternatives to use.
- Field Metal. This alloy of bismuth (32.5%), indium (51%) and tin (16.5%) becomes liquid at 60 ºC, so it is used for industrial molding and prototyping, or as a non-toxic replacement for Wood’s metal.
- Galinstano. It is an alloy of gallium, indium and tin, one of the alloys with which it has been tried to replace the uses of alloys with mercury (toxic). It is liquid at room temperature and is more reflective and less dense than mercury. It also has applications as a refrigerant.
- Rose Metal. Also known as Rose alloy, It is an alloy widely used in welds and fusions. It is composed of bismuth (50%), lead (25%) and tin (25%).
- NaK. This alloy of sodium (Na) and potassium (K) is a highly oxidizing substance, capable of releasing large amounts of caloric energy (exothermic). A few grams in contact with oxygen in the air is enough to start a fire. Even so, this alloy is liquid at room temperature and is used as an industrial catalyst, coolant or desiccant.
- Vital. It is a refractory alloy of cobalt (65%), chromium (25%) and molybdenum (6%) as well as other minor elements (iron, nickel). It was first developed in 1932 and is highly usable due to its lightness and extreme resistance to corrosion and temperature.