Creep of cryogenic steels and alloys

Reviewed are the mechanisms of metal and alloy creep of cryogenic temperatures. Four thermally activated processes are proposed as possible creep mechanisms, namely, 1. cross slip; 2. moving dislocations intersections with the forest of dislocation, resulted in step formation; 3. friction in the lattice conditioned by the Pierls forces; 4. nonconservative movement of thresholds. The prevailing effect of the one of the above mechanisms depends on the temperature interval of loading and on the material structure. Noted are the peculiarities of the austenite metastable steels (Kh18N9T,Kh25N20) creep conditioned by the formation of martensite under low-temperature loading. A conclusion is made that it is possible to prevent from the excessive creep in the above steels using stoppage in loading, heating, followed by cooling and loading up to the initial stress