LAUSR

The characteristic dislocation structures are developed in metals during cyclic deformation. Some studies have implied that the dislocation structures affect the fatigue strength. Yokoi et al.1) reported that the formation of a dislocation cell structure is suppressed in an Fe–1.5 mass%Cu alloy showing a higher fatigue strength than Fe. Ushioda et al.2) also found that dislocation cells are hard to form, and dislocation veins and dislocation walls are preferentially formed in Fe alloys containing 0.5–1 mass% of Si, which are known to have a higher fatigue strength than Fe. Shuto and Yokoi3) compared the fatigue limit and the dislocation structures of an Fe–0.5 mass%Si alloy and an Fe–2 mass%Ni alloy at the same plastic strain amplitude. They reported that the dislocation walls tend to be formed, and the cell structure development is restricted at a total strain amplitude of 3 × 10 −3 in the Fe–0.5 mass%Si alloy, whereas the cell structure was easy to be formed in the Fe–2 mass%Ni alloy. As a result, the fatigue limit of the Fe–0.5 mass%Si alloy became longer than that of the Fe–2 mass%Ni alloy. These results implied that the fatigue limit of Fe may possibly be increased if the development of dislocation structures can be controlled, and the cell structure Formation Mechanism of Dislocation Walls during Cyclic Deformation in an Fe–Si Alloy