ISO 6892-4:2015 specifies the method of tensile testing of metallic materials in liquid helium (the boiling point is 269C or 4,2 K, designated as 4 K) and defines the mechanical properties that can be determined.

This part of ISO 6892 may apply also to tensile testing at cryogenic temperatures (less than 196C or 77 K), which requires special apparatus, smaller test pieces, and concern for serrated yielding, adiabatic heating, and strain-rate effects.

To conduct a tensile test according to this part of ISO 6892 at 4 K, the test piece 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.

NOTE The boiling point of the rare 3He isotope is 3,2 K. Usually, the tests are performed in 4He or a mixture of 3He and 4He with a high concentration of 4He. Therefore, the temperature is, as designated before, 4 K.