EXAMINATION OF ELECTRON BOMBARDMENT HEATING FOR EFFECTS ON THE TENSILE PROPERTIES OF TUNGSTEN.

The effects of heating with 10-kv electron beams were studied by comparing the tensile properties of tungsten heated by electron bombardment and by thermal radiation. Bombarded specimens with both undisturbed and visibly damaged surfaces were tested at both room and high temperatures. At 2200C the ultimate tensile strength obtained when heating by thermal radiation was found to be the same as the strength obtained when heating by electron bombardment. Also, prolonged bombardment heating at 2400C under conditions not producing any surface changes prior to testing did not influence the tensile properties when compared to heating by thermal radiation. Normal strengths were reduced by bombardment only when surfaces were visibly damaged, the reduction being greatest at room temperature and considerably less at the higher temperature. The modes of fracture and the microstructure of failed specimens were independent of the means of heating. On the basis of these results it appears that electron bombardment heating, if properly applied, can be used in conducting valid mechanical property tests at high temperatures. Author