Mechanical hysteresis in beryllium single crystals oriented for (1010) (112o) slip

Abstract

The temperature dependence of the friction stress for (1010) (1120) type dislocations in beryllium has been measured in the range 300-500 K. For each temperature investigated, the friction stress was computed from the maximum loop width and the corresponding irreversible work data, obtained from the family of closed hysteresis loops developed by the cyclic compression of appropriately oriented single crystals. In addition, the values were also determined using the alternative method involving the elastic limit as obtained by extrapolation of the maximum shear stress against the maximum loop width curve to zero loop width. Both methods of analysis give essentially the same results. The data show that the friction stress for this system decreases in an almost linear fashion with increasing temperature from 0.28 kg mm^-2 at 300 K to 0.13 kg mm^-2 at 500 K. In magnitude, these values are approximately five times the corresponding values previously reported for (0001) (1120) type dislocations in beryllium.