This International Standard specifies the method of tensile testing of metallic materials in liquid helium (boiling point at − 269 °C or 4,2 K, designated as 4 K) and defines the mechanical properties that can be determined. This International Standard may also apply to tensile testing at cryogenic temperatures (less than − 196 °C or 77 K), which requires special apparatus, smaller specimens, and concern for serrated yielding, adiabatic heating and strain rate effects. To conduct a tensile test at 4 K in accordance with this International Standard, the specimen installed in a cryostat is fully submerged in liquid helium (He) and tested using displacement control at a nominal strain rate of 10− 3 s− 1 or less. Tests using force control or higher strain rates are not considered.