SEM-ECC Investigation of Dislocation Arrangements in Cyclically Deformed Copper Single Crystals with Different Crystallographic Orientations

The fatigue limits of copper single crystals cyclically deformed at constant plastic strain amplitudes

“…The quite distinctive value of the fatigue limit between the two oriented crystals is due to the formation of diOE erent dislocation structures, that is vein structures in the [034] crystal (Gong et al 1996) and irregular labyrinth structures in the [017] crystal (Li et al 2001). It seems that the fatigue limit varies from values close to that of single-slip crystals to that of polycrystals, when the orientation changes from [011] to [001].…”

“…Recent work revealed that the dislocation structures, which formed in the ‰1 112Š crystal deformed cyclically at a lower strain amplitude of 3:7 £ 10 ¡4 , consist primarily of vein structures and quite a few PSB ladder structures that are just in the initial stage of formation (Li et al 2001). It can thus be inferred that the dislocation structures of the ‰1 112Š crystal consist only of vein structures at even lower strain amplitudes, that is the fatigue limit.…”

“…This implies that the fatigue limit, de®ned as the threshold strain amplitude below which PSBs do not form, can be determined to be about 6 £ 10 ¡5 for a copper single crystal oriented for single slip (Laird 1976). Recently, systematic studies on copper single crystals oriented for double or multiple slip (Gong et al , 1996 1995) and, more recently, Li et al (1998Li et al ( , 1999aLi et al ( ,b,c,d,e,f,g, 2000Li et al ( , 2001 indicated that the crystallographic orientation in double-or multiple-slip-oriented crystals has a strong eOE ect on the cyclic deformation behaviour of copper single crystals, and that cyclic deformation behaviour of some double-or multiple-slip-oriented copper single crystals is, to a certain extent, similar to that of polycrystals. How does the crystallographic orientation aOE ect the fatigue limit of cyclically deformed copper single crystals?…”

Effect of orientation on cyclic stress–strain curves and dislocation patterns of Ag and Cu single crystals

“…They found that the plateau behavior also appeared in [0 1 1] Cu single crystals, which is similar to that of single-slip oriented one. Based on a plenty of experimental results from different oriented Cu single crystals, Li et al [19][20][21][22][23][24] proposed a general conclusion on orientation effect of Cu single crystals. They suggested that when the crystallographic orientation changes from single-slip orientation to double-slip orientation, even to multiple-slip orientations, the plateau behavior of Cu single crystals will gradually disappear and the saturation resolved shear stress will increase obviously, especially at higher strain amplitude.…”

Effect of Pre-Fatigue on the Monotonic Deformation Behavior of a Coplanar Double-Slip-Oriented Cu Single Crystal

“…Actually, the dislocation structures induced by fatigue deformation are quite different, strongly depending upon the crystallographic orientation (especially for double-slip orientations) [7][8][9]. As differently-oriented Cu single crystals are adopted for fatigue pre-deformation treatments, the induced dislocation structures are different; in this case, it is important to know how the corresponding static mechanical properties will change.…”