H.D. Bauer

Ultrafine nanostructure of partially crystallized bulk amorphous Zr54.5Ti7.5Al10Cu20Ni8

Bulk amorphous Zr54.5Ti7.5Al10Cu20Ni8 was investigated by means of small-angle neutron scattering and high-resolution electron microscopy. Partially crystallized states were generated by annealing. The scattering data were analyzed in terms of a model taking into account both properties of the particles and interparticle interference. The mean radius of the particles is 1.3 nm. They are surrounded by a depletion zone with mean thickness of 2.6 nm. The volume fraction of the particles is estimated from the interparticle interference effect; its upper limit after annealing at 653 K for 4 h is 12%. Electron microscopy confirms the size determined from the scattering data and shows that the particles are crystalline.

Insight into the Formation of Ultrafine Nanostructures in Bulk Amorphous Zr(54.5)Ti(7.5)Al(10)Cu(20)Ni(8)

Abstract : Bulk amorphous Zr(54.5)Ti(7.5)Al(10)Cu(20)Ni(8) is investigated by means of small-angel neutron scattering (SANS) diffractional-scanning calorimetry (DSC) high-resolution electron microscopy (HREM) and other methods. The formation of ultrafine nonstructures in the glassy phase is observed and explained by a new model. Structural fluctuations of randomly distributed partially ordered domains grow during annealing just below the glass transition temperature by local re-ordering. During annealing the DSC gives evidence for a increasing volume fraction of the locally ordered domains. At high volume fractions of impinging domains a percolation threshold on the interconnected domain boundaries occurs and enhanced diffusion becomes possible. At that stage SANS measurements lead to statistically significant scattering data. The SANS signals are analyzed in terms of a model taking into account spherical particles surrounded by diffusion zones and interparticle interference effects. The mean radius of the nanocrystalline particles is determined to 1 nm and the mean thickness of the depletion zone is 2 nm. The upper limit for the volume fraction after annealing at 653 K for 4 hours is about 20%. Electron microscopy confirms the size and shows that the particle ant crystalline.