Evidence for cooling-rate-dependent icosahedral short-range order in a Cu–Zr–Al metallic glass

摘要

Samples of Cu_(47.5)Zr_(47.5)Al_5 metallic glass were prepared at different cooling rate, R. The dependence of the X-ray diffraction patterns on R was analysed by comparing them with corresponding patterns of computer-simulated models generated at different cooling rates as well. The observed changes in the experimental diffraction patterns are reproduced by the simulations, showing an increasing fraction of icosahedral clusters with decreasing cooling rate. The difference of the fractions of icosahedrally coordinated atoms in mould-cast and rapidly quenched Cu_(47.5)Zr_(47.5)Al_5 averages to 3 (1)%. Different frozen-in thermal displacements and different density are ruled out as a possible origin for the experimental observations.