Thermal hardening of Ni3Ge alloy single crystals with an L1(2) superstructure at low temperatures

The mechanical properties and the dislocation structure of Ni3Ge alloy sing le crystals have been experimentally studied at low temperatures. It is fou nd that the flow stresses increase beginning with 4.2 K, and the observed r ise in the stresses depends on the orientation of the strain axes of the cr ystals. The dislocation structure is investigated thoroughly. It is reveale d that the mean density of dislocations and the interdislocation interactio n parameter alpha anomalously increase as the temperature increases in the range 4.2-293 K. The mechanisms providing an explanation for the temperatur e anomaly of flow stresses and the alpha parameter are considered. The acti vation energy of thermal hardening is evaluated. It is assumed that the low activation energies of thermal hardening are due to the motion of dislocat ions at velocities close to the velocity of sound at these temperatures. (C ) 2000 MAIK "Nauka/Interperiodica".