A NEW INTERMETALLIC PHASE IN AG-BI ALLOY PRODUCED BY PRESSURE-TEMPERATURE ACTION

The simple eutectic Ag-Bi alloy system exhibits under pressure-tempera ture action an intermediate phase of composition Ag3Bi. The crystal st ructure of the new phase was investigated in metastable state under am bient conditions by X-ray powder diffraction. An orthorhombic (distort ed hexagonal close-packed) structure of an ordered type was derived wi th lattice parameters a = 3.089 Angstrom, b = 4.847 Angstrom, c = 5.89 2 Angstrom and space group Pmm2, similar to the corresponding phase in the Ag-Sb system. The new phase decomposes into the eutectic two-phas e state Ag + Bi by annealing. The atomic ratios are analyzed as Hume-R othery criterion for formation of intermediate phases. (C) 1998 Elsevi er Science Ltd. All rights reserved.