Refraction (metallurgy)
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In metallurgy, refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory. These metals derive their high melting points from their strong intermolecular forces. Large quantities of energy are required to overcome intermolecular forces. The strong intermolecular forces are a result of metal bonds. In metal bonds, electrons in the metal atom's outermost shell become de-localized, forming a pool of free electrons and ionized atoms. This is also why metals are good conductors.
Some refractory metals include molybdenum, niobium, tungsten, and tantalum. These materials are also noted for their high elastic modulus and hardness.
Hafnium carbide is the most refractory binary compound known, with a melting point of 3890 degrees C.[1][2]