Phase separation and crystallization in the bulk amorphous alloy Zr41Ti14Cu12.5Ni10Be22.5

The decomposition and crystallization above the glass temperature of the bulk metallic glass Zr41Ti14Cu12.5Ni10Be22.5 and the crystallization during solidification of the melt were investigated by means of different analytical methods, including Transmission Electron Microscopy (TEM), Small Angle Neutron Scattering (SANS), Field Ion Microscopy with Atom Probe (FIM/AP). Dependent on the thermal history these phase transitions lead to different phases and different microstructures of the alloy. During annealing above the glass temperature the decomposition of the alloy into two supercooled liquid phases is observed by the formation of nanosized precipitates, which differ from the matrix by their Be and Ti contents. This decomposition retards significantly the subsequent crystallization, however it does not inhibit the formation of the phases which crystallize if the decomposition is bypassed by appropriate heat treatment. By stepwise crystallization a nanosized microstructure is formed consisting of three metastable phases and of stable Zr2Cu. This microstructure differ significantly from the crystalline equilibrium microstructure result from slow cooling of the melt. Crystallization of the amorphous alloy by very fast heating causes totally different microstructures