DESIGN OF A HOT TENSILE STAGE FOR AN ULTRA-HIGH-VOLTAGE ELECTRON-MICROSCOPE AND ITS APPLICATION TO IN-SITU DEFORMATION OF SAPPHIRE AT 1620-K AND 1720-K

A hot tensile stage, which is capable of operation at temperatures of up to 2300 K, has been constructed for an ultra-high-voltage (3 MV) electron microscope. With this stage, in situ deformation experiments have been conducted on sapphire at 1620 and 1720 K. At 1620 K, almost all the dislocations activated are of the basal slip system. The motion of dislocations is not jerky but rather smooth and continuous. At 1720 K, dislocations frequently undergo motions not confined in the basal plane. Activation of the secondary slip system is also observed at this temperature.