Review of High Cycle Fatigue Properties of Structural Materials at Cryogenic Temperatures

Abstract

Using a new system installed in 1983 at NRIM, we have carried out a high cycle fatigue test at liquid helium temperature. Based on our experimental data, high cycle fatigue properties of some titanium alloys and austenitic steels at cryogenic temperatures (at 4 K, 77 K and 293 K) are outlined in this paper. Generally the S-N curves shifted to a higher stress level at lower temperature, and they were almost parallel. As a result, the fatigue strength at 10⁶ cycles increased in proportion to a gain in strength by temperature decrease. In Ti-6A1-4V forged alloys and JN1 steel, however, the difference of S-N curves among the three temperatures became narrower as the N_f increased and a fatigue limit was hardly seen. During cryogenic high cycle fatigue for the titanium alloys and some austenitic steels, subsurface crack initiation apparently occurred without the existence of any defects like inclusions and pores. The microstructural origin of subsurface crack initiation and relevant deformation behavior are also examined.