Liquid-quenched Ag-Ge alloys; formation and evolution of metastable phases

Abstract

The formation and decomposition behaviour of metastable structures in liquid-quenched (LQ) Ag-Ge alloys was studied with X-ray diffraction, resistivity measurements and TEM techniques. Pure Ag and alloys containing 7, 10, 15, 20 and 22.5 at. % Ge were studied. Upon LQ, pure Ag and 7 and 10 at. % Ge alloys yield a single f cc phase; 15 and 20 at. % Ge alloys give a mixture of two metastable phases (f cc and h cp); and the Ag-22.5 at. % Ge alloy gives a metastable h cp phase. Also, the first evidence of an amorphous phase in as-LQ Ag-22.5 at. % Ge alloy is presented. It is shown that Ag-rich f cc phase can retain up to ∼ 20at. % Ge in solid solution. Furthermore, stacking faults play an important role in the formation and decomposition of metastable phases in the Ag-Ge system.