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In this work, axial cooling rates during solidification in the Fe-25Ni (wt.%) suction-cast alloy were evaluated based on cellular spacing measurements. Good agreement of the experimental results with the 20/{d(cm)}2 relationship was observed for the standard water-cooling system temperature of 17 ± 1 °C. The importance of this casting parameter is reported for the first time. A linear decrease in the cooling rate with increasing water-cooling system temperature is demonstrated and at least 20% lower values are expected for a temperature increase by 10 °C compared to standard conditions. Furthermore, the cooling rate exponentially decreases with increasing rod diameter for all water-cooling system temperatures. A new expression for cooling rates during solidification, taking into account the casting parameter (WCST expressed in K), i.e. C R = 10 - 0.0059 ⋅ W C S T + 4.9746 { d ( m m ) } 0.0195 ⋅ W C S T - 3.6351 , is proposed. The reliability and benefits of this formula have been demonstrated by casting the Zr50Cu40Al10 glass-forming alloy at various water-cooling system temperatures.

The effect of yttrium additions on the glass formation of the Zr50Cu40Al10 alloy with high oxygen content was investigated. Unlike other reports showing the positive effect of alloying Zr-based alloys with a few percent of rare earth elements, we examined the Y-to-oxygen ratios. As calculated, a stoichiometric amount of yttrium (2808 at ppm) is required to bind all the oxygen (4212 at ppm) to form the Y2O3. Additionally, the influence of half (1404 at ppm) and double stoichiometric (5616 at ppm) levels of yttrium, with respect to the measured oxygen content to be bound was evaluated. The Y-doped alloys were synthesized by arc melting, followed by suction casting into copper molds with conical and rod cavities. The critical diameter of the undoped alloy was below 3 mm, while stoichiometric and double stoichiometric yttrium concentrations allowed to obtain 5 and 7 mm diameter glassy samples, respectively. Microstructure observations confirmed the scavenging effect of yttrium, leading to the formation of a cubic ( $$ Ia\bar{3} $$ I a 3 ¯ space group) yttrium sesquioxide. The glass forming ability of the alloys was additionally determined based on differential thermal analysis, allowing to propose the best indicator for the studied Zr-Cu-Al alloys.

The mechanical properties of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy were presented, with an emphasis on the strain rate effect and presence of crystalline inclusions on the deformation and fracture mechanisms. X-ray diffraction studies indicated fully amorphous alloy structures with lower oxygen contents and partial crystalline structures at higher oxygen levels; however, completely different compressive deformation behaviour was observed. Uniaxial compression tests of the fully amorphous alloy showed elastic deformation, followed by yielding, distinct plastic deformation and serration flow behaviour. An increase in strain rate from 1×10–4 to 1×10–2 s–1 did not affect the yield strength; however, it decreased the compressive fracture strength and reduced the plastic strain. Scanning electron microscopy (SEM) observations with energy dispersive spectroscopy (EDS) analysis showed that the intermetallic CuZr2 phase was present even in the low oxygen content alloy, leading to lower fracture strength and ductility loss. For the high oxygen level samples, the presence of the dendritic Zr51Cu28Al21 phase was confirmed, leading to fracture strength impairment. The difference between ductile and brittle samples has been reflected on the fracture surfaces. The higher the plastic strain was, the higher the density of shear bands forming during deformation manifested by a serration flow behaviour on stress–strain curves.

As it is known, the glass forming ability of Zr-based alloys is very sensitive to oxygen content. Oxygen contamination may come from raw zirconium and from alloy preparation stages as well. This work was focused on both factors. Using inert gas fusion method authors measured oxygen content in the zirconium delivered by five different providers as well as in five cone-shaped ingots after a full preparation process. Oxygen level influence on the critical diameter of Zr48Cu36Al9Ag7 alloy was quantitatively determined by cone test. Several common thermal indicators using characteristic temperatures were also calculated. They mostly exhibited high sensitivity to oxygen level as their correlation with the critical diameter was very high. Obtained results revealed that zirconium purity is not a relevant parameter in its quality description. The main GFA influencing factor is oxygen contamination level which should never be neglected. Moreover, an in-depth analysis including cost/quality aspects has been conducted in order to obtain practical guidelines for Zr-based bulk metallic glasses preparation.

The effect of oxygen content on the glass forming ability of the Zr50Cu40Al10 alloy is presented. Two different oxygen levels, 194 ± 26 wt. ppm and 918 ± 72 wt. ppm, in the arc melted and suction cast alloys were obtained using Zr metal of different forms and nominal oxygen contents. Critical diameters for glass formation were determined by microstructural observations of cast conical and rod-shaped samples. Their structures were further investigated by X-ray diffraction. The critical diameter of the alloy with the lower oxygen content was 8 mm, while for the higher oxygen content it was below 3 mm. For the latter, the τ3 (Zr51Cu28Al21) crystalline inclusions were observed in the central part of the 3 mm diameter sample. The fully amorphous samples exhibited a large supercooled liquid range and a high reduced glass transition temperature.

The effect of iron addition on the microstructure of the Cu-Zr-Al-Y glass-forming alloy was studied. Despite a high superficial cooling rate, small Fe additions (1.5 and 3 pct) induced formation of crystalline CuZr and AlCu2Zr phases on the outer layers of suction-cast rods. As the melt composition near the solid/liquid interface was depleted in Fe, the remaining melt vitrified at a relatively low cooling rate.

In this work, the effect of boron content on the high temperature wetting behavior in the Si-B alloy/h-BN systems was experimentally examined. For this reason, hypoeutectic, eutectic and hypereutectic Si-B alloys (Si-1B, Si-3.2B and Si-5.7B wt %, respectively) were produced by electric arc melting method, and then subjected to sessile drop/contact heating experiments with polycrystalline h-BN substrates, at temperatures up to 1750°C. Similar to pure Si/h-BN system, wetting kinetics curves calculated on a basis of in-situ recorded drop/substrate images point towards non-wetting behavior of all selected Si-B alloy/h-BN couples. The highest contact angle values of ~150° were obtained for hypoeutectic and eutectic Si-B alloys in the whole examined temperature range.