2001 年 42 巻 1 号 p. 74-84
Cyclic deformation of ultra-fine grain (UFG) materials processed by severe plastic deformation is reviewed in light of recent experimental results and common concepts of fatigue. High strength bulk metals with a characteristic structural element size of 200–300 nm were obtained through the so-called equal-channel angular pressing (ECAP) technology. Fatigue properties are discussed in terms of stress-controlled and strain-controlled fatigue. Enhancement of fatigue life under constant stress amplitude is emphasized in comparison with some shortening in fatigue life under constant plastic strain amplitude. Fine structure and surface morphology of post-fatigued materials are characterized on different scale levels to account for the fatigue behaviour observed. Mechanisms of fatigue in ECA-processed materials are discussed within frameworks of a simple one-parameter model of dislocation kinetics.
