Preliminary field-ion microscope study of grain-boundary junctions in tungsten

A field-ion microscope capable of operation at up to 80 kV has been used to study grain-boundary junctions in hot-drawn tungsten wire. At the high operating voltages available in this instrument, images of three or more grains and at least one grain-boundary junction were frequently observed. The grain-boundary geometry at the junctions imaged in four separate specimens was analyzed and an estimate made of the relative grain-boundary energies. The relative energies were then correlated with the observed angular misorientations and boundary planes and the results compared with the predictions of the coincidence and 0-lattice models for grain boundaries in single-phase polycrystals. Statistical analysis of the data strongly suggests that an apparently low grain-boundary energy in tungsten can be correlated with specific coincidence relations, although detailed predictions from the models have not been confirmed