Preliminary characterization of the intermetallic 'YNi' obtained by both mechanical grinding and alloying

The intermetallic compound YNi and the (Y+Ni) mixture were submitted to a high-energy milling process under argon atmosphere. X-ray powder diffraction and microprobe analysis revealed in both cases the formation of a new phase 'YNi'. Its structural properties were different from those of the YNi as-cast sample (orthorhombic FeB type) and presented some similarities with GdNi (orthorhombic CrB type) milled under the same conditions. The application of isostatic pressure on the YNi as-cast sample gives a comparable result. This non-equilibrium material 'YNi' still exists even after annealing treatments performed up to 873 K. The presence of air during milling leads to the formation of a mixture of (oxy)nitride Y(O.N) and Ni metal and the new phase 'YNi' is not synthesized under such conditions. Also, the influence of the milling process on the magnetic properties of similar compounds such as GdNi and ErNi is discussed. (orig.)