Cobalt - ₂₇Co: physical properties

Cobalt is a brittle, hard, silver-grey transition metal with magnetic properties similar to those of iron (it is ferromagnetic). It has a high melting point and is hard-wearing even at high temperatures. Its alloys also possess useful properties and so it finds use in high speed steels and cutting tools for instance. The physical properties of cobalt resulted in its use in a cobalt-chromium-molybdenum alloy (Vitallium, 1937) that is strong, has a good corrosion resistance and is tolerated by the body. These days cobalt alloys are used less as they are heavy.

Density properties

• Density of solid: 8900 kg m^‑3
• Molar volume: 6.67 cm³

Elastic properties

• Young's modulus: 209 GPa
• Rigidity modulus: 75 GPa
• Bulk modulus: 180 GPa
• Poisson's ratio: 0.31 (no units)

Hardnesses

• Mineral hardness: 5.0 (no units)
• Brinell hardness: 700 MN m^-2
• Vickers hardness: 1043 MN m^-2

Electrical properties

• Electrical resistivity: 6 × 10^‑8 Ω m; or mΩ cm

Heat and conduction

• Thermal conductivity: 100 W m^‑1 K^‑1
• Coefficient of linear thermal expansion: 13.0 × 10^‑6 K^‑1

Optical properties

The image above is a virtual representation of cobalt metal calculated by Patrick Callet using the complex diectric function of the element only.

• Reflectivity: 67 %
• Refractive index: (no data) (no units)

Acoustic properties

• Velocity of sound: 4720 m s^‑1