The recrystallization of commercially pure and doped tungsten wire drawn to high strain
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The recrystallization processes in both undoped and doped tungsten wire a f t e r drawing to a true strain of 7.7 were examined by light microscopy and transmission electron microscopy. High a n g l e g r a i n boundary migration commenced at approximately the same temperature in both materials, but proceeded much more rapidly in the undoped wire, where the absence of a potassium bubble dispersion allowed a c o a r s e r , more e q u i a x e d g r a i n structure to f o r m . No change from the (110) deformation texture was observed in either c a s e . Recrystallization in the undoped wire was dominated at lower temperatures (1100 to 1200°C) by the growth of l a r g e g r a i n s into a much f i n e r structure. As the ann e a l i n g temperature was increased, this process was replaced by a g e n e r a l g r a i n coarsening which eventually produced a relatively equiaxed recrystallized g r a i n structure. It a p peared probable that it was the second phase dispersion inhibition alone that prevented s i m i l a r structural changes in the doped w i r e .
AN
examination of recent reports concerning the recrystallization of doped tungsten wire1-s shows that although an improved g e n e r a l understanding of this subject has been achieved, many of the detailed aspects of this process r e m a i n inadequately understood. It appeared probable that an investigation by t r a n s mission electron microscopy of annealed undoped tungsten wire would permit the identification of recrystallization processes in doped tungsten which were not uniquely associated with a dispersed second phase. Consequently, observations of the recrystallization of 0.18 mm undoped, commercially pure tungsten wire were compared t o s i m i l a r data obtained previously for doped tungsten wire of the same size. 8 Such a comparison was of particular interest, because e a r l i e r r e p o r t s 9'1° suggested that the mechanisms of recrystallization in these two materials m i g h t be very similar, in s p i t e of their l a r g e difference in recrystallized g r a i n structure.
EXPERIMENTAL PROCEDURE Samples of undoped and doped tungsten (General E l e c t r i c Type 218) were warm worked without i n t e r mediate anneals t o a true strain of 7.7 (0.18 mm diam) by the same standard c o m m e r c i a l procedure in each c a s e .11 T h e s e specimens were furnace annealed in 1.3 × 10-s P a vacuum for 1 h at various temperat u r e s from 600 t o 2150°C. The rate of heating was
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