| The cyclic deformation features of low stacking fault energy materials are not clearly understood and the available reports up to date are not consistent and sometimes even contradictory to each other. Some controversies about the cyclic hardening behavior in planar slip f.c.c metals partly originated from extremely low work hardening rate and frequent strain bursts, which maintain the stress level close to the critical resolved shear stress for a long period of time. In this paper, the effects of stacking fault energy and alloying elements on the cyclic deformation behavior and slip mode of f.c.c metals are reviewed. An attempt is also made, using available data, to develop a quantitative criterion which predicts the slip mode from wavy to semi-planar to planar slip with alloying in cyclic deformation of alloys. Since the repeated reversal of dislocation motion with cycling increases the chance of mutual trapping and annihilation, the solute content above which only planar slip behavior is observed usually increases dramatically in cyclic deformation. The low energy clustered dislocation structures such as cells, loop patches and/or ladder structure can be gradually formed from the initially planar microstructure if the strain amplitude is high enough to induce more active to-and-pro motion of dislocations during cycling of semi-planar slip alloys. The prediction on the transition of slip mode is compatible with most of the data on fatigue of Cu-Al and Cu-Zn alloys. |
|
