Influence of milling conditions on the segregation-induced instability of Pd3Zr

摘要

Structural transformations in Pd3Zr intermetallid upon ball-milling and subsequent annealing was studied under different milling conditions. The compound was milled in a medium energy vibrating mill with tungsten-carbide vial and ball as well as in a high energy planetary mill with stainless steel components. The milling processes were performed in highly purified Ar gas and in a mixture of Ar+10%H gases, respectively. The as-milled powders were annealed in the temperature range of 500-1300°C, and the structural transformations were studied by X-ray diffraction with monochromatic Cu Kα1 radiation. It is shown that the impurities introduced from milling components and the oxygen contamination from milling atmosphere strongly influence the stability of the nanocrystalline Pd3Zr during the mechanical- and subsequent heat treatments. The evolution and coexistence of Pd(Zr) with Pd3Zr, induced by the preparation and annealing processes, are discussed.