Mechanical alloying and magnetic saturation of tungsten-nickel powders

Alloying mechanism and magnetic saturation of tungsten and W-40 wt.% Ni milled powders were investigated using XRD, SEM and saturation magnetisation techniques. Mechanical alloying was proceeded by deformation of FCC Ni toward FCT phase and BCC to BCT in W, hence formation of supersaturated tetragonal Ni(W) solid solution. Milling of pure W yielded a product comprised of magnetic BCT and non-magnetic nanocrystalline BCC W powders. The magnetic saturation of W increased at the early milling stage and decreased later due to the transition of the BCC W structure toward anisotropic close packed crystal structure and formation of nanograins with high specific surface. Magnetic saturation of W-Ni powders decreased with milling time but increased after forming a metastable tetragonal solid solution. (C) 2011 Elsevier Ltd. All rights reserved.