Structural characterization of mechanically milled and annealed tungsten powder

Nanocrystalline W powders with an average crystallite size of about 50 nm were produced by mechanical milling. BCT phase was mechanically induced as a result of BCC lattice deformation (compression) along [110], upon 10 h, 20 h and 30 h milling corresponding to a magnetic saturation of 1.3, 6.9, and 9.8 μTm3/kg. This BCT phase suggests the tetragonal deformation path to be responsible for the observed anomalous magnetism in W. Following DSC–TG thermal analysis, a magnetic saturation of 68 μTm3/kg was obtained upon annealing the 30 h milled W powder at 1200 °C. In addition, two BCT phases with c/a = 1.313 (a = 0.29066, c = 0.38170 nm) and 0.907 (a = 0.32602, c = 0.29575 nm) were detected.

XRD patterns of W (a) milled for 0, 10, 20, 30 h, (b) annealed at 1100 °C and (c) annealed at 1200 °C.Figure optionsDownload as PowerPoint slideHighlights
► Nanocrystalline W powders with D = 50 nm were produced by MM.
► BCT phase was induced due to compression of BCC lattice along [110].
► 10, 20 and 30 h milled powder yielded magnetic saturation of ~ 1, 7 and 10 μTm3/kg.
► Tetragonal deformation path is responsible for observed anomalous magnetism in W.
► Upon 1200 °C annealing, a magnetic saturation of 68 μTm3/kg was obtained.