Fatigue of polycrystalline zirconium in the temperature range of 4.2 to 293 K

Fatigue fracture console bending of polycrystalline electron-beam melted zirconium (Rsub(239K)/Rsub(4.2K)=170) in a wide range of stress amplitudes at 4.2, 77 and 293 K is studied. A gap on the fatigue curve at 4.2 K associated with transition from multicycle mechanism of fatigue fracture to the small-cycle one is revealed. A decrease of Zr durability not described earlier with a test temperature decrease from 293 to 77 K is noted in a certain range of stress amplitudes. It is shown that this phenomenon is connected with prevailence of twinning as a main deformation mechanism at the initial stages of plastic deformation at 77 K as compared with advantageous slip at 293 K