X-RAY-DIFFRACTION STUDY ON ULTRAFINE PARTICLES OF AG-CU ALLOYS PREPARED BY HYDROGEN PLASMA-METAL REACTION METHOD

A series of ultrafine particles (UFP) in AgxCu100-x alloys was prepared by the "hydrogen plasma-metal" reaction method with changing composition x(b) of bulk parent alloys. The changes in diffraction profiles and lattice constants on x(b) were investigated by X-ray diffraction and least-squares pattern fitting methods. On the Cu-rich side (x(b) < 50), the UFP was composed of three metastable phases: Cu-rich 1 phase (x = 6.1 approximately 5.3), Cu-rich 2 phase (x approximately 12.2) and Ag-rich phase (x = 94.8 approximately 91.0). In these, the solubility of Ag in the Cu-rich 2 phase was about 2.5 times as large as the maximum value (x = 4.9) at the eutectic temperature of the equilibrium phase diagram. On the Ag-rich side together with x(b) = 50, the UFP was composed of Cu-rich 1 phase (x approximately 5.3) and Ag-rich phase (x approximately 91.7) except for x(b) = 90. The total concentration of Ag in the UFP noticeably deviated positively from x(b).