PHASE EVOLUTION DURING ION-BEAM MIXING OF AG-CU

Ion-beam mixing of the immiscible Ag-Cu alloy system was investigated using 1.0 MeV Kr ion irradiation at temperatures ranging from 80 to 47 3 K. Mixing of binary (80 nm Cu/55 nm Ag) and multilayer [(8.5 nm Cu/1 2.2 nm Ag)X11] samples was characterized by backscattering spectrometr y, electrical resistivity, and x-ray diffraction. Below room temperatu re, the Ag-Cu system is rendered completely miscible by Kr irradiation with the formation of a simple homogeneous phase. For irradiation at 473 K, the system again becomes immiscible, but with enhanced solubili ties in the two terminal phases. At intermediate temperatures, two or three phases are formed, a nearly equiatomic phase, and one, and somet imes two, terminal phases. Irradiation at elevated temperatures of sam ples completely mixed at low temperature led to the decomposition of t he near equiatomic phase; the new steady states were nearly the same a s those obtained by direct irradiation of an as-deposited sample. Phas e formation depended only weakly on the ion flux, although at the high er temperatures the decomposition reaction was favored by lower ion fl uxes. The experimental results are explained using a diffusion model b ased on a competition between cascade mixing and thermally activated d emixing. (C) 1997 American Institute of Physics.