Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group differs. The most common definition includes five elements: two of the fifth period and three of the sixth period. They all share some properties, including a melting point above 2000 °C and high hardness at room temperature. They are chemically inert and have a relatively high density. Their high melting points make powder metallurgy the method of choice for fabricating components from these metals. Some of their applications include tools to work metals at high temperatures, wire filaments, casting molds, and chemical reaction vessels in corrosive environments. Partly due to the high melting point, refractory metals are stable against creep deformation to very high temperatures.
Filament of a 200 watt incandescent lightbulb highly magnified
Apollo CSM with the dark rocket nozzle made from niobium-titanium alloy
A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically ductile and malleable. These properties are the result of the metallic bond between the atoms or molecules of the metal.
Iron, shown here as fragments and a 1 cm3 cube, is an example of a chemical element that is a metal.
A metal in the form of a gravy boat made from stainless steel, an alloy largely composed of iron, carbon, and chromium
Gallium crystals
A metal rod with a hot-worked eyelet. Hot-working exploits the capacity of metal to be plastically deformed.