The mechanical behavior of beryllium is important in a range of Department of Energy (DOE) weapons applications. In this study the authors determine quantitatively the texture as a function of processing history in specimens cut from three vacuum hot pressed (VHP) block beryllium grades S200-D, -E, and P31664 which have been used in various components over the years. Hot pressing of metal powders has been known to produce preferential alignment of crystals during formation. Moreover, it has been shown that the standard production method of beryllium powder creates anisomorphic grain shape and preferred alignment of crystals. The vintages in this study were hot-pressed from processed beryllium powder, and therefore texture was anticipated. The billets were sectioned for time-of-flight (TOF) neutron diffraction measurements to allow comparison of microstructural differences between vintages. Neutron diffraction is ideal for investigating structural properties in beryllium because the neutron absorption of beryllium is negligible and bulk (2 cm3) specimens can therefore be investigated. Moreover, the polychromatic TOF radiation in this study provides significant statistical advantages for texture measurements compared to the traditional method of monochromatic x-ray diffraction. Even order harmonic coefficients are extracted from a combination of 50-60 TOF neutron diffraction spectra containing a total of 40000-60000 data points via a Rietveld refinement method. S200-D, -E, and P31664 beryllium blocks from the Los Alamos archive develop simple fiber texture with (0001) fiber axis offset from the hot-pressing direction when manufactured by powder processing methods and VHP consolidation. For both S200-D and S200-E vintages sharp fiber texture follows Braun-type attrition. The S200-F vintage possesses a broader starting fiber texture, due to powder processing by impact grinding. Evidence from difference pole figures suggests powder procedures of the sort in this study impose a starting fiber texture before consolidation and that texture strength and symmetry in beryllium is dependent on details of powder processing in addition to the consolidation method.
Texture development in S200-D, -E and P31664 beryllium blocks from neutron diffraction spectra
Bestimmung der Texturentwicklung in S200-D, -E und P31664 Berylliumblöcken mit Hilfe der Neutronenbeugung
Scripta Materialia ; 40 , 7 ; 825-830
1999
6 Seiten, 2 Bilder, 22 Quellen
Article (Journal)
English
Neutron diffraction texture analysis of multi-phase systems
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