Concentration and temperature dependence of decomposition in supercooled liquid alloys

Small-angle neutron scattering experiments were performed on the bulk amorp hous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1(R), 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 Zr46.8Ti8.2C u7.5Ni10Be27.5 (Vit4(R)). The small-angle neutron scattering data of the sa mples, annealed at temperatures between 603 K and 663 K, show interference peaks, giving evidence for spatially correlated arrangements of inhomogenei ties. The Q values of the interference peaks, Q(max), decrease with increas ing annealing temperature T a and, at a given annealing temperature, with c omposition following the connecting line from Vit1 to Vit4. Down to the gla ss transition temperature T-g, the data follow a relation 1/L-2 proportiona l to (T-s - T-a) as predicted by the linearized Cahn theory, with L = 2 pi/ Q(max) the characteristic wavelength of the decomposition and T-s the appa rent spinodal temperature. Below T-g, a different behavior is observed, whi ch may be either due to a change in atomic diffusion or due to an insuffici ent relaxation of the samples.