HIGH-TEMPERATURE IN-SITU STRAINING EXPERIMENTS IN THE HIGH-VOLTAGE ELECTRON-MICROSCOPE

Design rules are described here for high-temperature straining stages for transmission electron microscopy. Temperatures above 1000 degrees C can be attained by electron bombardment of the specimen grips. Therm al equilibrium can be reached in a short time by carrying off the heat by water cooling. Some applications of this stage are described. Ferr oelastic deformation was observed at 1150 degrees C in t' and partiall y stabilized zirconia, which changes the microstructure for successive dislocation plasticity. In the oxide-dispersion-strengthened alloy IN COLOY MA 956, dislocations are impeded by oxide particles and move smo othly between the particles. At high temperatures, both the resting an d traveling times control the average dislocation velocity. In MoSi2 s ingle crystals of a soft orientation, dislocations with 1/2[111] Burge rs vectors are created in localized sources and move on {110} planes i n a viscous manner. The dislocations in Al-Pd-Mn single quasicrystals are oriented in preferred crystallographic directions and move in a vi scous way as well. On the basis of in situ observations, conclusions a re drawn for interpreting macroscopic deformation behavior at high tem peratures.