Recrystallization and texture formation in cold-rolled dysprosium sheet
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The p r i m a r y recrystallization of dysprosium can be characterized by an apparent activation energy of 13.4 • 1.4 kcal/mole when specimens are isothermally annealed at t e m p e r a tures between 400 and 600~ At temperatures between 300 and 400~ recrystallization is strongly retarded, possibly by precipitation, and the activation energy associated with the p r o c e s s is increased to 31.4 + 4 kcal/mole. The deformation texture of dysprosium sheet following a cold reduction of 50 pct can be described as (0001). STUDIES of the r a r e earth metals have most often dealt with the magnetic properties of single crystal and polycrystalline specimens which exhibit interesting and complicated " s p i r a l " magnetic structures and magnetic transitions over certain temperature ranges. 1 However, the v e r y high ferromagnetic saturation magnetization of the r a r e earths compared to the transition metals 2 is of more practical significance. For example, the substitution o f gadolinium or dysprosium for iron c o r e s in cryogenic rotating apparatus or t r a n s f o r m e r s would greatly increase the flux carrying capacity of the magnetic circuits. Potentially large size reductions in equipment then could be made. The magnetic properties of core materials are optimized by rolling-annealing cycles that produce grain orientations (textures) in which the easy magnetization directions are preferentially aligned along some axis, e . g . , the well known (110)[001] texture of 3 pct Si-ironfl The mechanical properties 4-7 and isochronal annealing s of several r a r e earth metals have been investigated and the effects of working and annealing on the permeability of gadolinium have been identified. 9 Virtually nothing is known, however, about the deformation and annealing textures or recrystallization kinetics of the r a r e earth metals, 1~factors which might ultimately determine the feasibility of these materials for magnetic applications. The purpose of this investigation was to quantitatively c h a r a c t e r i z e the development of p r e f e r r e d orientation and the response to annealing of a typical r a r e earth metal, dysprosium. EXPERIMENTAL PROCEDURE Research Chemicals Corporation supplied the s t a r t ing material for all experiments: hot rolled dysprosium strips 3 in. • 1 in. by 0.060 in. thick. The material is nominally 99.9 pct pure; the major impurities r e vealed by our spectrographic and vacuum fusion analyses are oxygen and nitrogen (Table 19, common contaminants in all the r a r e earth metals not subjected to special processing, n The strips were cold rolled on a Stanat four high mill R. H. HOPKINS is Fellow Engineer, Westinghouse Research Laboratories, Pittsburgh, Pa. 15235. Manuscript submitted April 16, 1973. METALLURGICAL TRANSACTIONS
(2.5 in. diam work rolls, 8 in. diam back-up rolls) to 10, 20, 30, 40, 50 and 60 pct of their original hot-rolled thickness. The material was reduced at a rate of 0.002 in. per pass to r e t a r d cracking. The strips were not r e v e r s e d between passes nor w
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