Comparison of the decomposition and crystallization behavior of Zr and Pd based bulk amorphous alloys

The best metallic glass formers known so far are Vit1 (and similar alloys with a slight variation in composition) and Pd40Cu30Ni10P20. having critical cooling rates of about 1 Ws and glass transition temperatures T-g of around 636 K and 582 K, respectively, at a heating rate of 10 K/min. To compare the decomposition and crystallization behavior of these alloys, we performed small-angle neutron scattering (SANS) on the Vit1 derivative Zr42.6Ti12.4Cu11.25Ni10Be23.75 (Vit1A) and on Pd40Cu30Ni10P20 (PCNP) at temperatures near their T-g. The samples of Vit1A show interference peaks when annealed for several hours between 603 K and 643 K, giving evidence for decomposition on the nanometer scale. The SANS intensity monotonically increases in this temperature regime. An in-situ experiment, performed for 15 h at 621 K, with an average acquisition time of 20 min, resolves the time evolution of this decomposition. The SANS experiment on PCNP shows a completely different behavior. An in-situ SANS experiment performed on PCNP for 10 h at 571 K produced no scattering, but the SANS intensity changed drastically when the temperature was raised to 586 K. However, no interference maximum was observed in the SANS data for PCNP. X-ray diffraction data, measured after the in-situ experiments, resolve nanocrystals in Vit1A but a coarse-grained structure in PCNP.