TEMPERATURE DEPENDENCE OF MICRO-YIELDING AND TRANSITION TO MACRO-STRAIN FOR TUNGSTEN

Micro-strain in polycrystalline tungsten was found to be dependent on the square of applied stress from 4·2°K to 298°K for a wide range of impurity and dislocation content. Source activation was consistent with the double kink nucleation mechanism above 78°K and below this temperature the possibility of stress activated dislocation tunnelling was considered. The energy barrier associated with the Peierls hills was determined to be ≅0·85 ev. The transition from micro-strain to macro-strain was governed by the dynamic interaction of mobile dislocations with the b.c.c. tungsten lattice and with random impurities. © 1969 Taylor & Francis Group, LLC.