Cyclic deformation behavior of double-slip-oriented copper single crystalsIII: conjugate double slip orientation on 001-(1)over-bar11 side of the stereographic triangle

The cyclic deformation behaviors of [(2) over bar 23] and [(1) over bar 12] conjugate double-slip-oriented copper single crystals were investigated at constant plastic shear strain amplitude gamma(pl) in the range of about 10 (-4)-10(-2) at ambient temperature in air. The results of [(1) over bar 17] and [001] crystals are included for comparison. Unlike the plot of initial hardening rate theta(0.2) against gamma(pl) of the [(2) over bar 23] cryst al which does not exhibit two obvious regions, the plot for the [(1) over b ar 12] crystal exhibits two regions similar to those in single-slip-oriente d crystals. The cyclic stress-strain (CSS) curve of the [(1) over bar 12] c rystal shows a clear plateau over the range of about 5.0 x 10(-4)-4.0 x 10( -3), which is narrower than that of the single slip crystals (6.0 x 10(-5)- 7.5 x 10(-3)) although the saturation shear stress is nearly the same. Howe ver, no obvious saturation phenomenon was observed in the cyclically deform ed [(2) over bar 23] crystals over the range of plastic strain amplitude in vestigated. Even though the orientations of [(1) over bar 12], [(1) over ba r 17] and [(2) over bar 23] crystals are on the same side of the stereograp hic triangle, their plateau behaviors in the CSS curve are quite different, i.e. the plateau regions of the CSS curves for the crystals located on bot h sides of the [(1) over bar 12] crystal tend to die out except that an obv ious plateau region occurs in the cyclically deformed [(1) over bar 12] cry stals. The results above are mainly attributed to the rather different slip deformation characteristics associated with the different crystal orientat ions. In addition, two types of deformation bands DBI and DBII, formed in t he cyclically deformed [(1) over bar 12] and [(2) over bar 23] crystals, we re also discussed in terms of crystallographic geometry. (C) 1999 Elsevier Science S.A. All rights reserved.