The authors report complementary use of high-energy x-ray and neutron diffraction to probe the local atomic structure in a Zr-based bulk metallic glass. By analyzing the partial coordination numbers, the authors demonstrate the presence of multiple types of solute-centered clusters in the multicomponent glass and efficient packing of the amorphous structure at atomic scale. The authors’ findings provide a basis for understanding how local structures change during phase transformation and mechanical deformation of multicomponent amorphous alloys. © 2007 American Institute of Physics. [DOI: 10.1063/1.2742315]

Six La-based La-Al-Ni-Cu-(Co) alloys were subjected to a systematical study of glass formation by Bridgman unidirectional solidification at growth velocities between 0.1 and 4.82 mm/s at a temperature gradient of 15 K/mm. With increased Cu content the critical growth velocity for glass formation in La55Al25Cu20-xNix (x=0-20) alloys shows a steep minimum at 10 at.% Cu, indicating the largest glass forming ability for the La55Al25Ni10Cu10 alloy. However, replacement of Ni by Co leads to a further decrease in the critical cooling rate for the La55Al25Ni5Cu10Co5 alloy. Critical cooling rates for glass formation in the present alloys were also obtained through a study of their melting and solidification behaviors by thermal analytical measurement. The e.ect of alloying addition and the significance of reduced glass transition temperature for the glass forming ability of these alloys is discussed. c1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.

A conceptual approach to evaluate glass-forming ability for various glass-forming systems has been proposed from a physical metallurgy point of view. It was found that the glass-forming ability for noncrystalline materials was related mainly to two factors, i.e., 1/(Tg + Tl) and Tx (wherein Tx is the onset crystallization temperature, T g the glass transition temperature, and Tl the liquidus temperature), and could be predicated by a unified parameter γ defined as Tx/(Tg +Tl). This approach was confirmed and validated by experimental data in various glass-forming systems including oxide glasses, cryoprotectants, and metallic glasses.

Glass transition and crystallization behavior of Mg75Ni10Nd15 metallic glass has been studied by a temperature-modulated differential scanning calorimeter (TMDSC) and a normal differential scanning calorimeter (DSC). The truly vitreous state of the as-spun Mg75Ni10Nd15 alloy was confirmed by the direct observation of the glass transition through TMDSC measurements, which was not perceptible in the normal DSC heating scans. It was concluded that the glass transition signal was concealed by the relatively strong concurrent signal of the primary crystallization. This was further confirmed by the fact that the glass transition was revealed by both TMDSC and DSC for the samples with negligible heat release from the primary crystallization.

A family of inexpensive, Al2O3-forming, high–creep strength austenitic stainless steels has been developed. The alloys are based on Fe-20Ni-14Cr-2.5Al weight percent, with strengthening achieved through nanodispersions of NbC. These alloys offer the potential to substantially increase the operating temperatures of structural components and can be used under the aggressive oxidizing conditions encountered in energy-conversion systems. Protective Al2O3 scale formation was achieved with smaller amounts of aluminum in austenitic alloys than previously used, provided that the titanium and vanadium alloying additions frequently used for strengthening were eliminated. The smaller amounts of aluminum permitted stabilization of the austenitic matrix structure and made it possible to obtain excellent creep resistance. Creep-rupture lifetime exceeding 2000 hours at 750°C and 100 megapascals in air, and resistance to oxidation in air with 10% water vapor at 650° and 800°C, were demonstrated.