Composition Dependence Of Glass Forming Ability Research Articles

Atomic-Scale Mechanisms of the Glass-Forming Ability in Metallic Glasses

The issue, composition dependence of glass-forming ability (GFA) in metallic glasses (MG), has been investigated by systematic experimental measurements coupled with theoretical calculations in Cu-Zr and Ni-Nb alloy systems. It is found that the atomic-level packing efficiency strongly relates to their GFA. The best GFA is located at the largest difference in the packing efficiency of the solute-centered clusters between the glassy and crystal alloys in both MG systems. This work provides an understanding of GFA from atomic level and will shed light on the development of new MGs with larger critical sizes.

On the glass-forming ability of Ni–P binary alloys

The composition dependence of glass-forming ability (GFA) of Ni–P binary alloys was systematically examined by fabricating ribbons of different thicknesses, and the microhardness of the glassy ribbon was measured. The eutectic alloy Ni80.4P19.6 has the best GFA and the highest microhardness in glassy state. As the alloy composition is deviated from the eutectic composition, both GFA and microhardness decrease, accompanied with an increasing full width at half maximum of the main broad peak in the X-ray diffraction spectrum of the glassy ribbon. All these results indicate a close correlation among microstructure, GFA and microhardness for the metallic glass.

Glass-forming ability of soda lime borate liquids

We investigate the composition dependence of glass-forming ability (GFA) of a series of iron-containing soda lime borate liquids by substituting Na2O for B2O3. We have characterized GFA by measuring the glass stability against crystallization using a differential scanning calorimeter (DSC). The results show that the GFA decreases when substituting Na2O for B2O3. Moreover, we find that there is no direct link between the kinetic fragility and GFA for the soda lime borate series studied herein. We have also discovered and clarified a striking thermal history dependence of the glass stability against crystallization. In particular, the two glasses containing 20 and 25 Na2O mol% do not exhibit crystallization exotherms during the second DSC upscan at 10 and 20K/min following prior slow (10 and 20K/min) downscans. This indicates that the glass stability of these compositions can be enhanced by cooling their melts to the glassy state slowly, before any reheating. We explain this phenomenon in terms of the thermal history dependence of boron speciation.

Optimal glass-forming composition and its correlation with eutectic reaction in the Ti–Ni–Al ternary system

The composition dependence of glass-forming ability was investigated for the Ti-Ni-Al ternary alloys. Glassy ribbons were fabricated via single-roller melt spinning. The optimal glass-forming composition was located at Ti(54)Ni(32)Al(14), with a critical thickness of about 90 mu m for complete glass formation. With respect to the Ti-Ni binary alloy, Al addition in the system only marginally improves the glass-forming ability. It is attributed to a small atomic size difference between Ti and Al. For the Ti(54)Ni(32)Al(14) alloy, together with the binary eutectic Ti(76)Ni(24) and hypereutectic Ti(68)Ni(32) alloys for comparison, phase selection in the arc-melted ingots was investigated. The optimal glass-forming composition, Ti(54)Ni(32)Al(14), is near the univariant eutectic groove of [L --> Ti(Al)(2)Ni + beta-Ti(Al)] in the phase diagram. It is suggested that if the primary crystallization of the Ti(2)Ni intermetallic can be suppressed, solidification of deeply undercooled melt will undergo such a eutectic reaction prior to glass formation. (C) 2008 Elsevier B.V. All rights reserved.