Cu60Zr30Ti10 Bulk Metallic Glass Research Articles

Formation and Corrosion Behavior of Mechanically-Alloyed Cu–Zr–Ti Bulk Metallic Glasses

Cu60Zr30Ti10 metallic glass powder was prepared by mechanically alloying a mixture of pure Cu, Zr, and Ti powders after 5 h of milling. Cu60Zr30Ti10 bulk metallic glass (BMG) was synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass powder at 746 K in the pressure range of 0.72–1.20 GPa, and the structure was analyzed through X-ray diffraction and transmission electron microscopy. The pressure could enhance the thermal stability, and prolong the existence, of the amorphous phase inside the Cu60Zr30Ti10 powder. Furthermore, the corrosion behavior of the Cu-based BMG in four corrosive media was studied using a potentiodynamic method. The Cu60Zr30Ti10 BMG exhibited a low corrosion rate and current density in 1 N solutions of H2SO4, NaOH, and HNO3. X-ray photoelectron spectroscopy results revealed that the formation of Zr- and Ti-rich passive oxide layers provides a high corrosion resistance against 1 N H2SO4 and HNO3 solutions, and the breakdown of the protective film by Cl− attack was responsible for pitting corrosion in a 3 wt % NaCl solution. The formation of oxide films and the nucleation and growth of pitting were analyzed through microstructural investigations.

Consolidation of Mechanically Alloyed Cu-Zr-Ti Metallic Glass Powders

In the present study, Cu60Zr30Ti10 metallic glass powders were prepared by mechanical alloying of pure Cu, Zr, and Ti powder mixtures. Cu60Zr30Ti10 metallic glass composite powders were obtained after 5 h of milling as confirmed by X-ray diffraction and transmission electron microscopy. The metallic glass powders were found to exhibit a supercooled liquid region before crystallization. Cu60Zr30Ti10 bulk metallic glass were synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass powders at 723 K in the pressure range of 0.72 ~ 1.20 GPa. Cu60Zr30Ti10 BMG with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix was successfully prepared under applied pressures. It was found that the pressure could enhance the thermal stability and prolong the existence of amorphous phase inside Cu60Zr30Ti10 powders.

Enhancement of solderability of Cu60Zr30Ti10 bulk metallic glass by dealloying in hydrofluoric acid solution

To extend the engineering applications of bulk metallic glasses (BMGs), it is necessary to create process to form appropriate BMG/BMG and BMG/crystalline metal joint. In this study, hydrofluoric acid (HF) solution treatment and a laser soldering process were employed to enhance the solderability of Cu60Zr30Ti10 BMG. The surface treatment in HF solution successfully dissolved surface Zr and Ti, resulting in concentration of Cu at the surface. A reflow soldering process using Sn-3.0 mass% Ag-0.5 mass% Cu (SAC) solder on this surface showed obvious dewetting because the thin Cu-rich layer dissolved into the molten solder. Laser soldering with a 0.01 s irradiation time, which produces rapid heating and cooling rates, offered good wettability of SAC solder and Sn-57 mass% Bi (SB) solder. At the interface between the SB solder and the HF-treated BMG foil, an intermetallic compound (IMC) layer was observed by scanning electron microscopy (SEM).

Improved wettability of Sn-based solder over the Cu60Zr30Ti10bulk metallic glass surface

The wettability of Pb-free Sn-based solder over the Cu-based Cu60Zr30Ti10bulk metallic glass surface was investigated. We observed that the as-polished surface was nonwetting for the solder, which was due to the surface oxide layer of ZrOxformed in air. After complete removal of the oxide layer, a thin layer of Ag was deposited on the clean Cu60Zr30Ti10surface. The Ag-covered Cu60Zr30Ti10surface showed relatively high resistivity to the reoxidation even in air, and thus the wettability of the Cu60Zr30Ti10surface for the Sn-based solder was greatly improved.

Improved oxidation resistance of Cu60Zr30Ti10 BMG with plasma immersion ion implantation

The influences of nitrogen ion implantation on the Cu60Zr30Ti10 bulk metallic glass were investigated. It was found that the surface composition and structure of the nitrogen-ion implanted metallic glasses were different from those of the as-cast one and the oxidation resistance was improved by the surface modification process. Grazing incidence X-ray diffraction (GIXRD) showed that the implanted samples remained amorphous but with some ZrO2 and copper oxides on the surface. X-ray photoelectron spectroscopy (XPS) results further revealed that a thin ZrN layer is formed while no Cu atom can be observed on the top surface of the implanted samples. Thermogravimetric analysis (TGA) showed an improved oxidation resistance of the implanted samples compared with the as-cast metallic glass. Both as-cast and implanted metallic glasses formed ZrO2 and copper oxides after oxidation. This was consistent with our observations in scanning electron microscopy (SEM).

Oxidation-induced copper segregation in Cu60Zr30Ti10 bulk metallic glass

Copper segregation in a subsurface layer during annealing of Cu60Zr30Ti10 bulk metallic glass at 773 K under oxygen atmosphere has been investigated by x-ray diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. The formation of metallic copper is strongly dependent on the annealing environment. Various oxides with metallic copper are formed after annealing in oxygen atmosphere, but only crystalline intermetallic phases are found under vacuum annealing. Besides, surface characterization results show that the sample annealed in oxygen and vacuum result in enrichment and depletion of Cu on the surface region, respectively.

Effects of alloying on oxidation of Cu-based bulk metallic glasses

The oxidation kinetics and the effects of alloying on the oxidation behaviors of copper-based bulk metallic glasses were studied. The oxidation kinetics, oxide compositions, and structures were investigated by thermogravimetric analysis (TGA), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Both the TGA results and the XPS depth profile measurements showed that the oxidation resistance of Cu60Zr30Ti10 bulk metallic glass was improved by adding Hf, but it deteriorated when it was alloyed with Y. The oxide phases were found to be ZrO2, Cu2O, and CuO in samples heated at 573 K while an additional metallic Cu phase was detected in the ones heated at 773 K. A porous oxide structure was observed in the (Cu0.6Zr0.3Ti0.1)98Y2 metallic glass oxidized at 673 K, and the poor oxidation resistance of the alloy is attributed to the porous structure.

Oxidation Behavior of Cu60Zr30Ti10 Bulk Metallic Glass

The oxidation kinetics of Cu60Zr30Ti10 bulk metallic glass and its crystalline counterpart were studied in oxygen environment over the temperature range of 573–773 K. The oxidation kinetics, measured with thermogravimetric analysis, of the metallic glass follows a linear rate law between 573 and 653 K and a parabolic rate law between 673 and 733 K. It was also found that the oxidation activation energy of metallic glass is lower than that of its crystalline counterpart. The x-ray diffraction pattern showed that the oxide layer is composed of Cu2O, CuO, ZrO2, and metallic Cu. Cu enrichment on the topmost oxide layer of the metallic glass oxidized at 573 K was revealed by x-ray photoelectron spectroscopy while there was a decrease in Cu content in the innermost oxide layer. The oxide surface morphologies observed from scanning electron microscopy showed that ZrO2 granules formed at low temperatures while whiskerlike copper oxides formed at higher temperatures.

Abrasive wear of Cu60Zr30Ti10 bulk metallic glass

Abstract The abrasive wear behaviors of Cu 60 Zr 30 Ti 10 bulk metallic glass in different annealing states have been studied using pin-on-disc measurement. The volume loss increases with both sliding distance and applied load. The hardness of metallic glass increases with annealing temperature but their wear resistances are not directly proportional to hardness and do not follow the standard wear law. The wear rate increases in the order: 30% crystallized metallic glass, metallic glass and 50% crystallized metallic glass. The wear behavior of metallic glass is thought to be related to the wear mechanism involving crack initiation and propagation instead of simply on hardness. Worn surface under higher applied load shows that the metallic glass suffers from severe wear compared with that of annealed metallic glasses.