The microstructure of a melt-spun Zr28Ni44Cu28 (at. %) alloy was characterized in order to determine the structures and compositions of the crystalline phases that compete with glass formation during rapid solidification. Two crystalline phases were identified, namely, a face centered cubic (FCC) zirconium oxide phase and a primitive cubic version of the big-cube oxide phase, using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy techniques. Our results indicate that the Zr-O atomic pair interaction is preferential compared to the other atomic pair possibilities, supporting the formation of Zr-based oxides over the equilibrium phases in the ternary Zr-Ni-Cu system. Further, the results provide insight into the mechanisms of oxygen-induced crystallization in Zr-based BMGs and the corresponding decrease in glass forming ability (GFA) with increasing oxygen concentrations.

This study first reports details of a successful arc-melting furnace in the production of bulk metallic glasses (BMGs). Also, the study presents the results of a statistical experiment evaluating critical processing parameters that can increase oxygen concentration and its effects on the glass forming ability (GFA) of two Zr-based BMGs. The experiments on Zr48Cu46.5Al4Nb1.5 BMG composite found that using low arc-current (200 A), short melting time (11 s), positive pressure of argon inert gas trapped in the synthesis chamber, and the absence of prior melting of a Ti-getter results in a lower oxygen contamination in the produced alloy. The second experiment using the Vitreloy 105 BMG alloy proved the previous findings.

Abstract Zr-based bulk metallic glasses (BMGs) are widely used as mechanical components due to their excellent properties and high glass-forming ability. However, there is a lack of research concerning the tribological behavior of BMG versus BMG. The sliding characteristics of Vitreloy-105 (Zr52.2Cu17.9Ni14.6Al10Ti5 at.%) were studied in air using a pin-on-disk apparatus equipped for continuous measurement of friction force and without lubrication. The counterface material was the same BMG. The structure, thermal stability, and wear morphology were examined by X-ray diffraction, differential scanning calorimetry, non-contact profilometer, and scanning electron microscopy. For a normal load applied (10.0, 20.4 and 38.2 N) at constant 233 rpm the coefficient of friction ranged from 0.30 to 0.36 at steady state. Average wear rate was more pronounced on the pins under higher load and the predominant wear mechanism observed was adhesive, with presence of peeling-off and micro-cracks accompanied by some grooves and abrasive wear at lower loads.

The present work reports investigation on the Glass Forming Ability (GFA) of Zr-based Bulk Metallic Glasses (BMG’s) by microalloying with early transition metals. GFA was measured as the amorphous fraction formed in samples with different diameters using optical microscopy (OM) and image analysis techniques. Samples with the highest GFA had their oxygen content measured in a Leco RO-400. This study shows that additions of Molybdenum or Iron in a Zr48Cu(48-x)Al4Mx (M = Mo or Fe) alloys resulted in a minor GFA improvement, but far from the results reported in the literature with Nb additions in this system. Niobium microalloying to a Zr62Cu15.5Al10Ni(12.5-x)Nbx and (Zr55Cu30Al10)100-xNbx alloys have a deleterious effect on the GFA. Oxygen measurements of (Zr55Cu30Al10)99Nb1 and Zr62Cu15.5Al10Ni12.4Nb0.1 alloys have shown similar oxygen content, indicating that oxygen was not a limiting factor on this study. The amorphous fraction quantification from OM image analysis maintains the same fraction ratio from the heat released at the crystallization event from heating DSC analysis.