Electron Backscatter Diffraction Analysis on ${hbox {Nb}}_{3}{hbox {Sn}}$ and ${hbox {Nb}}_{3}{hbox {Al}}$ Multifilaments

摘要

Observations of fractured cross sections, which are frequently used to determine the grain size distribution in ${hbox {Nb}}_{3}{hbox {Sn}}$, cannot be performed for ${hbox {Nb}}_{3}{hbox {Al}}$ since transgranular fracture is the dominant fracture mode. Instead, we have evaluated the grain size of ${hbox {Nb}}_{3}{hbox {Al}}$ using electron backscatter diffraction (EBSD). To check the validity of EBSD analysis for A15 grain structures, bronze-route ${hbox {Nb}}_{3}{hbox {Sn}}$ filaments were also examined by EBSD. The deformation-and-transformation of bcc supersaturated-solid solution ${hbox {Nb}}{hbox {(Al)}}_{rm ss}$ was found not only to homogenize and refine the grain size of the resultant ${hbox {Nb}}_{3}{hbox {Al}}$ but also to increase a ratio of high angle grain boundaries to low angle grain boundaries. The texture studies were made by pole figure works: the ${hbox {Nb}}{hbox {(Al)}}_{rm ss}$ retains a $langle 110rangle$ fibrous texture as well as the filament barrier (Nb, Ta) does. The transformed ${hbox {Nb}}_{3}{hbox {Al}}$ also has the weak $langle 110rangle$ fibrous texture, whereas ${hbox {Nb}}_{3}{hbox {Sn}}$ has almost never texture. A clear relationship between $J_{c}$ and the inverse of grain size was not observed.