Concentration and temperature dependence of decomposition in supercooled liquid alloys

Abstract

Small-angle neutron scattering experiments were performed on the bulk amorphous alloy Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) (Vit1®, subscripts indicate at.%) and on other alloys, where the (Zr,Ti) and (Cu,Be) contents were varied by following the line in composition space connecting Vit1 and Zr_(46.8)Ti_(8.2)Cu_(7.5)Ni_(10)Be_(27.5) (Vit4®). The small-angle neutron scattering data of the samples, annealed at temperatures between 603 K and 663 K, show interference peaks, giving evidence for spatially correlated arrangements of inhomogeneities. The Q values of the interference peaks, Q_(max), decrease with increasing annealing temperature Ta and, at a given annealing temperature, with composition following the connecting line from Vit1 to Vit4. Down to the glass transition temperature T_g, the data follow a relation 1/L^2 ∝ (T_s – T_a) as predicted by the linearized Cahn theory, with L = 2π /Q_(max) the characteristic wavelength of the decomposition and T_s the apparent spinodal temperature. Below T_g, a different behavior is observed, which may be either due to a change in atomic diffusion or due to an insufficient relaxation of the samples.

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