Tungsten exists in two forms: α and β. Under standard conditions, i.e., room temperature and pressure, α-type tungsten exhibits a stable body-centered cubic structure. β-type tungsten, on the other hand, can only exist stably in an oxygen environment, and its stable range is limited to below 630°C. Above this temperature, it will irreversibly transform into α-type.
In addition, tungsten has excellent physical parameters, including high density (35g/cm³), high melting point (3422°C) and boiling point (5927°C). Its hardness is also quite impressive, reaching 5, and it has a low Poisson's ratio (28). In hardness tests, tungsten exhibits a Vickers hardness of 3430MPa and a Brinell hardness of 2570MPa. In addition, the thermal properties of tungsten cannot be ignored. Its heat of fusion is 3kJ/mol and its heat of vaporization is as high as 807kJ/mol.
