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To enhance weldability, this study used a Nd:YAG laser (which produces a faster thermal cycle) in combination with a liquid cooling device (LCD) to spot weld (Zr53Al17Co29)99Ta1 BMG. Here, an LCD was employed to provide a variety of initial welding temperatures (IWTs), with progressively lower IWTs from room temperature (RT) to -5 °C. After the welding process, the microstructure evolution (including parent material (PM), heat affected zone (HAZ), and weld fusion zone (WFZ)), glass forming ability (GFA), and mechanical property (microhardness) of the laser-welded samples were investigated. The results showed that two types of crystallines were observed in the HAZ after RT welding. The GFA indicators of the welded samples and microhardness in the HAZ were affected significantly. When the IWT decreased to 0 °C, the crystalline phase in the HAZ and WFZ were barely noticeable which resulted in a softer HAZ; the GFA indicator of the welded sample was not substantially different than that of the PM.

Electrochemical corrosion of as-cast and annealed zirconium-based bulk metallic glass (BMG) Zr48Cu36Al8Ag8 in 0.1 M NaCl solution was investigated in this work. The as-cast specimen, in complete amorphous form, contained null percent of crystal phase (denoted as 0C); however, the annealed ones contained 11, 25, 50, 75 and 100 % crystal phase (denoted as 11C, 25C, 50C, 75C and 100C, respectively) determined by the annealing duration of 0C specimen at 471 °C. Through monitoring of open circuit potential (OCP), measurements of direct-current polarization resistance (PR), Tafel plot (TP), cyclic anodic potentiodynamic polarization (CAPD), and electrochemical impedance spectroscopy (EIS), we found that the corrosion behavior of the Zr48Cu36Al8Ag8 was detremined by the the crystal phase present in the specemns dominated by the annealing durations. The corrosion resistance decreased in the order: 25C > 11C > 0C > 50C > 75C > 100C. This result revealed that the corrosion resistance inclined to be better and reached a mxmium with increasing the percentgae of the crystal phase from 0 to 25%; however, it decreased with further increasing the crystal phase over 25%. A corrosion mechanism is proposed to rationalize the sequence of corrosion resistance. According to the mechanism, the remained free volume and residual strain energy are responsible for the specimens containing crystal phase less than 25% (i.e., 0C, 11C and 25C); whereas crystal defects such as grain boundaries governed the corrosion of those containing crystal phase more than 25 % (i.e., 50C, 75C and 100C).

The (Ti40Zr10Cu36Pd14)100 − xSix (x = 0, 0·5, 1·0, 1·5) bulk metallic glass (BMG) rods with a diameter of 2–4 mm have been successfully fabricated by suction casting method and characterised. The X-ray diffraction results reveal that these entire (Ti40Zr10Cu36Pd14)100 − xSix alloy rods exhibit a typical amorphous diffraction pattern with only a broad maximum at 2θ∼40°. The optimum glass forming ability values γ and γm (0·430 and 0·774 respectively) occur at the (Ti40Zr10Cu36Pd14)99·5Si0·5 amorphous alloy. This suggests that the Si element present a positive effect on increasing glass forming ability in the Ti40Zr10Cu36Pd14 alloy system. The hardness of these Ti based BMGs exhibits an increasing trend with Si addition and saturated ∼710 HV. In addition, the result of compression test shows that the optimum mechanical property occurs at the (Ti40Zr10Cu36Pd14)99·5Si0·5 amorphous alloy, which presents 2050 MPa fracture strength and 8% failure strain.

Zr-based thin film metallic glass (TFMG), exhibiting the unique properties of good glass forming ability (GFA), corrosion resistance, and biocompatibility, can be applied in various novel fields of industries. An ultra-smooth surface is obtained with the TFMG coatings, which is beneficial to modify the work surface. Thus, TFMG can be extended to medical appliances, such as surgical blades and micro-surgery scissors. The aims of this study are to fabricate the Cu-containing Zr-based TFMG onto SUS304 plates and to investigate the surface physical properties and their antimicrobial effects. The chemical compositions of Zr–Cu–Ni–Al coatings are examined by a field emission electron probe micro-analyzer (FE-EPMA). The amorphous structures of all TFMG are characterized by the X-ray diffractometry. The surface properties are analyzed by an atomic force microscope (AFM) and a water contact angle goniometer for the 304 stainless steel substrate and Zr–Cu–Ni–Al TFMG. Liquid culture methods and plate counting methods are used to assess the antimicrobial performance of specimens. The antimicrobial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under the Japanese Industrial Standard JIS Z2801: 2000 is over 99%. The release of copper ion from TFMG specimen is determined by the inductively coupled plasma-mass spectrometer (ICP-MS) to evaluate the antimicrobial activity of Cu-containing Zr-based TFMG. The results show that the surface of SUS 304 stainless steel substrate can be modified with deposited Zr–Cu–Ni–Al TFMG, and their improved antimicrobial efficacy against those bacteria is attributed to their amorphous rough surface, hydrophobic properties and released copper ion. The TFMG developed in this study with adequate hardness, good adhesion ability and antimicrobial efficiencies can be used as a promising candidate to improve the surface properties of the medical appliances and also to reduce the possibility of nosocomial infection.

For further enhancing the fatigue properties of high-strength aluminum alloy, the coating, which was combined with a layer of 200 nm ZrCu-based metallic glass thin film (MGTF) coupled with 50 nm titanium thin film buffer layer, was applied to coat on the surface of 7075-T6 aluminum alloy by the DC sputtering method. The results show that the fatigue limit could be significantly improved from 150 MPa for the uncoated sample to 250 MPa (66.7% increase) for the samples coated with ZrCu-based MGTF. In parallel, the fatigue life of 7075-T6 aluminum alloy with ZrCu-based MGTF could be drastically improved 45 times at a stress level of 250 MPa than the bare one. The outstanding mechanical properties of ZrCu-based MGTF, such as high strength and good adhesion between the film and the substrate, are the key factors to enhance the fatigue resistance of the coated aluminum alloy.

To demonstrate the effect of processing on the microstructure and subsequent mechanical property of bulk metallic glasses, we prepared two alloys, Cu 47.5 Zr 47.5 Al 5 and Cu 47.5 Zr 48 Al 4 Co 0.5 , using two different designs of suction mold – one with a sharp inlet and one with a blunt inlet. The two alloys have been demonstrated previously to be ductile via phase transformation of the B2 phase and twin formation during plastic deformation. Microstructures of the as-cast as well plastically deformed samples, in particular, the size and distribution of the B2 phase, were examined using X-ray diffraction, scanning and transmission electron microscopy. Compressive tests were conducted on samples cast by different molds and their properties were found to closely correlate with the B2 morphology. Fluid dynamics during suction casting was also analyzed. Effects of Vena contracta, flow velocity, and Reynolds number were discussed and compared favorably with experimental observations.

A prominent Fe-base bulk amorphous steel (BAS) alloy which presents high glass forming ability (GFA), good corrosion resistance, superior mechanical properties and relative lower cost. The Fe 41 Cr 15 Co 7 Mo 14 C 21 − x B x Y 2 ( x = 5–10) BAS rods with a diameter of 2–6 mm, can be fabricated by the suction casting method. The highest GFA value can be obtained by adjusting the ratio of boron/carbon, reaching to the value of γ = 0.4 and γ m = 0.69 for the alloy composition of Fe 41 Ce 15 Co 7 Mo 14 C 12 B 9 Y 2 . Meanwhile, this alloy also presents very large supercooled liquid region up to 81 K, favourable to be fabricated into micro-surgery tools by thermoplastic forming. In addition, the Fe-base BAS alloy exhibits extremely high hardness around 1200 Hv. The anodic polarization measurement of the Fe-based BAS exhibits a higher corrosion resistance than 304 SS and 316 SS in the Hank’s balanced salt solution. The sharpness test results reveal that the Fe-based BAS blade exhibits much higher sharpness because of its lower surface roughness and higher hardness. Moreover, the Fe-base BAS blade presents much better durability on cutting testing, it can remain relatively sharper edge-tip with a low blade sharpness index (BSI) value of 0.38 (in comparison with the BSI value of 0.59 for commercial blades) after the cutting testing over 50 cm length.

To study the interfacial reaction of the ex-situ reinforced phase (Ta) of a Zr-based ((Zr48Cu36Al8Ag8)Si0.75 + Ta5) bulk metallic glass composite after laser spot welding, the interfacial regions of the reinforced phases located at specific zones in the welds including the parent material, weld fusion zone and heat affected zone were investigated. Specimen preparation from the specific zones for transmission electron microscopy analysis was performed using the focused ion beam technique. The test results showed that the reinforced phases in the parent material, weld fusion zone and heat affected zone were all covered by an interfacial layer. From microstructure analysis, and referring to the phase diagram, it was clear that the thin layers are an intermetallic compound ZrCu phase. However, due to their different formation processes, those layers show the different morphologies or thicknesses.

In order to improve the fatigue life of high strength aluminum alloy, a protection coating with 200 nm Zr-based metallic glass thin film (MGTF) coupled with 50 nm titanium thin film buffer layer was coated on the 7075-T6 aluminum alloy by DC sputtering. The results of four-point-bending fatigue test revealed that the fatigue life of 7075-T6 aluminum alloy with Zr-based MGTF could be improved by 30 times at a stress level of 250 MPa. The improvement of Zr-based MGTF coated samples in fatigue limit was 235 MPa (56.7% increase) in comparison with 150 MPa for the uncoated samples. The superior mechanical properties of Zr-based MGTF, such as high strength and good bending ductility, lower surface roughness, good adhesion between the film and the substrate, and high compressive residual stress are the key factors to improve the fatigue resistance of the coated aluminum alloy.

The bio-electrochemical response in simulated body fluid of the Zr53Cu30Ni9Al8 metallic glasses with different degrees of partial crystallization was systematically examined and discussed. Through thermal annealing, the volume fractions of the crystalline phases are determined to be 0, 34, 63, and near 100%. Based on the bio-corrosion voltage and current, as well as the polarization resistance, it is concluded that the fully amorphous alloy exhibits the highest bio-electrochemical resistance. With an increasing degree of partial crystallization, the corrosion resistance becomes progressively degraded. The passive current reveals that the fully amorphous metallic glasses can form a more protective and denser passive film on the metallic glass surface. The formation of reactive nanocrystalline phases in the amorphous matrix would reduce the bio-corrosion resistance.

This study aims to develop a new Ta–Zr–Cu–Al–Ag thin film metallic glass (TFMG). The Zr–Cu–Al–Ag TFMGs were fabricated by co-sputtering of a Zr–Cu–Al–Ag bulk metallic glass target and a 99.9 at.% Ta target, which was controlled under various DC power. A bipolar pulsed DC power unit was connected to the Zr–Cu–Al–Ag bulk metallic glass (BMG) target to avoid arcing. The chemical compositions of Ta–Zr–Cu–Al–Ag TFMGs were examined by an electron probe microanalyzer (EPMA). Nanoindentation and nanoscratch tests were adopted to evaluate the hardness, elastic modulus and adhesion properties of the TFMGs. The amorphous structures of all TFMGs were characterized by the X-ray diffractometry and transmission electron microscope. It was found that the Ta content ranging from 26 to 63 at.% played an important role in the mechanical properties of the TFMGs. Abrupt enhancements of the hardness and elastic modulus were observed for this Ta-based TFMGs as compared with the Zr–Cu–Al–Ag TFMG. Relative atomic distance calculated from the XRD patterns reached a good agreement with the trend of variation of elastic modulus. The values of critical loads, LC1 and LC2, increased with Ta contents in the Ta–Zr–Cu–Al–Ag TFMGs. In addition, the lighter and shorter crack was found for the Ta–Zr–Cu–Al–Ag TFMGs with higher Ta content. The crack propagation resistance (CPR) value was applied to probe the toughness of TFMG semi-quantitatively, revealing that TFMG with 63 at.% Ta possessed a CPR value six times higher than that of the TFMG with 26 at.% Ta.

A novel Ni-free Zr–Cu–Ag–Al ((Zr 48 Cu 36 Ag 8 Al 8 )Si 0.75 ) and a Zr–Cu–Ni–Al ((Zr 53 Cu 30 Ni 9 Al 8 )Si 0.5 ) bulk metallic glass (BMG), for comparison, were employed for Nd:YAG laser spot welding with three pre-selected energy inputs, including a low (6.2 J), a medium (8.0 J) and a high (9.2 J) energy input. After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's microhardness test. The results showed the Zr–Cu–Ag–Al BMG has better weldability than the Zr–Cu–Ni–Al BMG. No crystallization was observed in the weld fusion zones (WFZs) or heat-affected zones (HAZs) of the welds under three pre-selected energy inputs. Therefore, the GFA indices of Δ T x (Δ T x = T x − T g , T x is the crystallization temperature and T g is the glass transition temperature), γ ( γ = T x /( T g + T l ), T l is the liquidus temperature) and γ m ( γ m = (2 T x − T g )/ T l ), and the mechanical properties of the Zr–Cu–Ag–Al BMG welds did not differ significantly in comparison to the parent material (PM). For Zr–Cu–Ni–Al BMG, HAZ crystallization was unavoidable when a lower energy input was used; therefore, the GFA indices and mechanical properties of the weld were affected. Furthermore, when the GFA indices, Δ T x , γ and γ m , were used to predict the thermal stability of the BMG HAZs, Δ T x seemed to correspond more directly to the HAZ crystallization behaviors in this study. It was observed that the Δ T x value of Zr–Cu–Ag–Al BMG was about 26% higher compared to that of Zr–Cu–Ni–Al BMG.

The Ti/Zr-based metallic glasses (MGs) with various Cu contents are prepared, with nominal compositions of Ti45Zr40Si15 (Cu-free), Ti45Zr40Si10Cu5 (low-Cu), and Ti45Zr20Cu35 (high-Cu). The mechanical properties, corrosion resistance, and in-vitro biocompatibility of these MGs are investigated by means of nano-indentation, electrochemical analyses, MTS assays and inductively coupled plasma mass spectrometry, as well as in-vivo biocompatibility in terms of scanning electron microscopy, micro-CT scans and histological observations. The results show that the electrochemical activity and biocompatibility of the MGs are sensitive to the Cu content. Following the electrocorrosion tests, an increase in ion concentration is observed in high-Cu MG. Eight independent in-vitro tests show that the higher ion concentration leads to a lower cell viability. The twelve-week in-vivo tests show that the Cu-free MGs can be a promising material for developing bio-implants. The high-Cu MG would release Ti and Zr ions with insignificant Cu ion following corrosion testing, enhancing an increased local osteoclast activity.

This paper presents the in-vitro and electrochemical investigations of four metallic glasses (MGs) for finding potential MG-based bio-materials. The simulation body-fluid Hanks solution is utilized for testing the corrosion resistance of MGs, and microorganisms of Escherichia coli are used in testing the bio-toxicity. In addition, a simple cyclic voltammetry method is used for rapid verification of the potential electrochemical responses. It is found that the Zr-based MG can sustain in the body-fluid, exhibiting the best corrosion resistance and electrochemical stability. The microbiologic test shows that E. coli can grow on the surface of the Zr-based metallic glass, confirming the low cell toxicity of this Zr-based MG.

Zr-based bulk metallic glasses (BMGs) possess excellent unique properties, such as high mechanical properties, good corrosion resistance, long-term antimicrobial ability, and were considered as an ideal candidate for medical tools. In this study, self-made ZrCuAlAgSi BMG surgical blade and commercial martensitic steel blade with and without metallic glass thin film (MGTF) were carefully examined for their sharpness. The amorphous state of BMG and MGTF were ascertained by X-ray diffraction (XRD) and differential scanning carlorimetry (DSC) analysis. A specially designed indentation-cutting rig was established to evaluate the sharpness of each blade on cutting the soft rubber material. The sharpness was evaluated by the blade sharpness index (BSI) which represents the ratio of external work done by the load to the energy required to initiate a cut or crack inside given materials. Results of sharpness test reveal that both BMG blade and the MGTF coated blade exhibits much lower surface roughness at their tip-edge and smaller BSI values (0.25 and 0.23, respectively) than the commercial blade (∼0.34), which corresponds to 26.5% and 32% improvement on the sharpness, respectively.

Direct current electropulsing was used to improve the plasticity of (Zr53Cu30Ni9Al8)99.5Si0.5 bulk metallic glasses. After the electropulsing treatment, the specimen showed reductions in both the glass transition and the crystallization temperatures while retaining its amorphous structure, and both Young's modulus and the hardness decreased while the nanoindentation loading curve became more serrated. Using the bond-interface method and Vickers indentation, the treated specimen showed more branching of semi-circular shear bands and less radial shear bands compared to its as-cast counterpart. The possible plasticity enhancement mechanism of the electropulsing treatment was also discussed.

(Cu42Zr42Al8Ag8)100− x Si x (x = 0 ∼ 1) amorphous alloy rods of 2–6 mm diameter were prepared by Cu-mold drop casting. The thermal properties, microstructure evolution, and mechanical properties were studied by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), transmission electron microscopy (TEM), hardness test, and compression test. The XRD result revealed that all as-quenched (Cu42Zr42Al8Ag8)100−x Si x alloy rods exhibited a broad diffraction pattern in the amorphous phase. The (Cu42Zr42Al8Ag8)99.5Si0.5 alloy was found to possess the highest glass forming ability (GFA) as well as the best thermal stability among all tested samples. In addition, both its hardness and yield strength were increased by the microalloyed Si content. The fracture strength and the plastic strain of (Cu42Zr42Al8Ag8)99.5Si0.5 amorphous alloy can reach 2000 MPa and 3.5 %.

This study investigated the effects of the initial welding temperature (IWT) and welding parameters on the crystallization behaviors of laser spot welded (Zr53Cu30Ni9Al8)Si0.5 bulk metallic glass (BMG). After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's micro-hardness test. The results showed that the heat-affected zone (HAZ) crystallization seemed avoidable under the room temperature welding process. However, with a combination of a lower energy input (welding Condition C) and a lower IWT (at 0 °C), a crystallization-free HAZ was finally obtained. Using the above welding condition into the refined heat flow equation, a critical retention time of 79 ms for the crystallization temperature interval was estimated. Moreover, as the laser welded samples came to crystallization in the HAZ, it was observed that a higher content of spherical-type crystalline precipitates tended to result in a higher value of glass transition temperature, Tg. Therefore, the GFA indices, ΔTx, γ and γm, were reduced. Furthermore, it was found that the micro-hardness value in the HAZ crystallization area was decreased due to the massive cracks formed in most parts of the crystalline precipitates. For a crystallization-free HAZ, the hardness seemed unaffected.

Using pre-selected welding parameters, a crystallization-free weld for (Zr 53 Cu 30 Ni 9 Al 8 )Si 0.5 bulk metallic glass (BMG) was successfully produced by adopting a Nd:YAG pulse laser in combination with a liquid cooling device (LCD). When a LCD was employed, a faster cooling rate and shorter retention time for the crystallization temperature interval were produced, thus, no crystallization was observed in the weld fusion zone (WFZ) or heat affected zone (HAZ). The hardness in those areas did not differ significantly in comparison to the parent material (PM). For the room temperature laser weld (LCD was not employed), HAZ crystallization seemed unavoidable, although no crystallization occurred within the WFZ. The major crystalline phase in the HAZ was identified as Zr 2 Cu. When the precipitates were greater in the crystallized area (i.e., HAZ), cracks were more likely to form, thus, hardness in the area was decreased.

The effect of Si addition on the oxidation of (Cu43Zr43Al7Ag7)99.5Si0.5 bulk metallic glass (CZ43S-BMG) was investigated over the temperature range of 375–500 °C in dry air. The results generally showed that the oxidation rates of the CZ43S-BMG followed a multi-stage parabolic-rate law, and the oxidation rate constants (kp values) fluctuated with increasing temperature. It was found that the kp values of the CZ43S-BMG were slightly slower than those of the Si-free glassy alloy (Cu43Zr43Al7Ag7, named as CZ43-BMG). The scales formed on the CZ43S-BMG strongly depend on temperature, consisting of 3 different modifications of ZrO2 and CuO, and minor amounts of Cu2O (formed at T ≥ 425 °C) and Al2O3 (only detected at 500 °C). In addition, the glassy substrate remained amorphous nature at T ≤ 400 °C, while it transferred to the crystalline phases of Cu10Zr7, ZrAl, and ZrSi2 after the oxidation at higher temperatures.

In this study, the nanoindentation behavior of a Cu–Zr–Al–Ag bulk metallic glass was investigated at various loading rates. It is found that the load–displacement curve of indentation exhibits a significant serration of displacement jumps (pop-ins). The experiment data show that the depths of the pop-in site are a geometric series. The size of pop-ins increases with indentation depth but decreases with loading rate; a larger applied loading rate leads to smaller pop-ins during the indentation process. However, the experimental results indicate that the loading rate has no influence on the depth ratio of pop-in sites. FIB observation and TEM diffraction patterns show that the microstructure of the BMG material remained amorphous irrespective of the presence shear bands.

In this study, the Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 bulk metallic glasses (BMGs) with superior glass forming ability are made by Cu-mold casting and injection casting processes. Critical rod size of the Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 BMGs (base alloys) reached ∼4 mm in diameter. The results of Vickers indentation and compression tests of Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 alloy reveal that the mechanical performance of the BMG base alloy is brittle. The highest fracture toughness and plastic strain of the base alloy are only ∼9 MPa m 1/2 and ∼0%, respectively. SEM observation is followed after the mechanical properties tests. It showed that the dominant patterns of the fracture surface are the featureless mirror-like and river-like regions. For enhancing the mechanical properties of the base alloys, porous Mo particles are added to form Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 –Mo BMG composites (BMGCs). It is found that the fracture toughness and the fracture strength of the 30 vol.% Mo particles reinforced Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 BMGCs is promoted to ∼50 MPa m 1/2 and ∼1100 MPa. The observation of the fracture surface of Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 –30 vol.% Mo BMG composite via the compression test reveals that the shear bands and cracks propagation is resisted by the dispersion of Mo particles and secondary shear bands are formed during the plastic deformation. It is also observed that the fracture surface is occupied by vein-like pattern, instead of mirror-like region. Moreover, the plastic strain of the Mg 58 Cu 29.5 Y 6 Nd 5 Ag 1.5 –30 vol.% Mo BMG composite increased to ∼29%.

With unique properties such as high strength, amorphous alloys in the bulk form have been a focus for many studies in recent years. Yet, the amorphous alloys (metallic glass) in the thin film form have not received much attention. In this paper, we will review and report some important and interesting results obtained from these thin film metallic glasses in which unique physical and mechanical properties can be enhanced by changing their compositions and by the precipitation of nanoscale particles.

To generate a rapid welding thermal cycle for a (Zr 53 Cu 30 Ni 9 Al 8 )Si 0.5 bulk metallic glass (BMG) weld, the Nd:YAG pulse laser welding process with pre-selected welding variables is used in this study. The microstructure development and crystallization behavior in the weld fusion zone (WFZ) and the heat-affected zone (HAZ) are investigated by scanning electron microscopy (SEM), micro-area X-ray diffractometry (XRD) and transmission electron microscopy (TEM). From the results, it is observed that the HAZ is liable to crystallize, although no crystallization occurs within the WFZ. The spherical type crystalline phases (with a particle size of 20–200 nm) observed in the HAZ, which are rich in Zr, Cu and Ni, result in a change of chemical composition in this region. Furthermore, if the particle size in the crystallized area is greater than 50 nm, cracks may form.

Based on the thermodynamic calculation, two phase separated Zr-based BMGs (Zr63.8Ni16.2Cu15Al5 and Zr66Cu15.3Ni8.7Al10) which developed by the authors previous study were selected for investigating their crystallization behavior and thermal stabilities by means of differential scanning calorimetry (DSC), and X-ray diffractometry. The results show that the Zr66Cu15.3Ni8.7Al10 amorphous alloy exhibits higher GFA than the Zr63.8Ni16.2Cu15Al5 amorphous alloy. But the Zr63.8Ni16.2Cu15Al5 amorphous alloy presents higher activation energy of crystallization (227 kJ/mole and 188 kJ/mole for Zr63.8Ni16.2Cu15Al5 and Zr66Cu15.3Ni8.7Al10 BMGs, respectively). However, Zr66Cu15.3Ni8.7Al10 amorphous alloy contains less atomic percentage of Cu and Ni elements (with positive heat of mixing) may result in forming less volume phase separation as well less interface area between these separated amorphous phase. Overall, the Zr66Cu15.3Ni8.7Al10 amorphous alloy exhibits longer incubation time at higher annealing temperature in comparison with the Zr63.8Ni16.2Cu15Al5 amorphous alloy, suggesting that the amorphous alloy which contains fewer amounts of Cu and Ni elements would have better thermal stability.

In this study,the (FePt)94-xCu6Nbx (x=0, 2.87, 4.52, 5.67) alloy films were prepared by co-sputtering. The effects of Nb addition content and heat treatment on the microstructure and magnetic properties of the polycrystalline FePtCu films are reported. Our previous experiments showed that the ordering temperature of the (FePt)94Cu6 films reduced to 320 °C, which is much lower than that of the FePt alloy. However, the grain growth after heat treatment limited the practical application in recording media. By adding the Nb content in the (FePt)94Cu6 film, the grain sizes of the films can be adjusted from 50 to 18nm, even for the films annealed at temperature as high as 600°C. DSC traces of as-deposited disorder films at different heating rates, to evaluate the crystallization of the order phase, revealed that the addition of Nb enhanced the activation energy of ordering from 87 kJ/mol to 288 kJ/mol for the (FePt)94-xCu6Nbx (x=0 and 2.87, respectively) films. The reduction of the grain size and the corresponding increase in the activation energy of the Fe-Pt-Cu-Nb films might result from the precipitation of the Nb atoms around the ordering FePt phase. The (FePt)94-xCu6Nbx (x=2.87) film showed a coercive force of 13.4 kOe and the magnetization of 687 emu/cc.

The recent research and development on metallic glasses in Taiwan over the past decade is reviewed in this paper. The major focus was to develop tougher bulk metallic glasses (BMGs), bulk metallic glass composites (BMGCs), and thin film metallic glasses (TFMGs), mostly in Zr and Mg based systems. Due to the Taiwan industry characteristics, metallic glasses are favored in the application for micro-electro-mechanical systems (MEMS), including micro- or nano-imprinting for optoelectronic devices and hologram patterns.

Mg–Cu–Y–(Gd) alloy rods are made by arc-melting and injection casting methods in this research. The improvement of glass forming ability and mechanical properties by using Gd to substitute Y in Mg 58 Cu 31 Y 11 bulk metallic glasses (BMGs) is of interest. The results of thermal analysis present that the Mg–Cu–Y base alloys with the addition of 6 and 8 at% Gd are the best BMG former. The Vickers indentation tests and the compression tests are carried out in order to explore the mechanical properties of alloys. It reveals that there is no obvious change in Young's modulus (∼45 GPa) of the Gd-containing Mg-based BMG, in contrast with the base alloys. Vickers (micro-) indentation fracture toughness measurements are performed for comparison. Shear bands and the corner cracks around the inverted pyramind mark are showed. An average fracture toughness of Mg–Cu–Y–Gd alloy is calculated as ∼4 MPa m 1/2 , which is a little higher than that of base alloys studied in the paper. Meanwhile, the fracture surface of Mg-based BMGs is dominant by featureless mirror-like and river-like pattern. Only nano-scaled shear bands and vein patterns are displayed, indicating that the plasticity of the Mg–Cu–Y–Gd BMGs are shown in nano-scale indeed.

We have employed a thermodynamic-computation approach to identify the composition of the Zr–Cu–Ni–Al alloy system exhibiting a two-liquid miscibility phase equilibrium in the liquid-temperature region, which tends to favor the occurrence of the liquid-phase separation. Guided by these calculated diagrams, a Zr-based alloy with a 10 at.% Al is designed, and its bulk-metallic glass (BMG) is prepared successfully by the copper-mould suction casting. A heterogeneous microstructure characterized by the existence of phase-separated regions with several to decades micrometers in size forms in the BMG. Under uniaxial compressive loading, the designed Zr-based BMG demonstrates the continuous “work hardening” and remarkable macroscopic plastic strain at room temperature. The improvement of mechanical properties is attributed to the unique glassy structure correlated with both the heterogeneous microstructure and the micro-scaled phase separation, leading to the extensive shear-band formation, interaction, and multiplication.

Mg 58 Cu 31 Gd 11 and Mg 65 Cu 25 Gd 10 alloys were synthesized via two processing routes, injection casting and melt spinning. The diameter of the injection-cast bars was 4 mm in diameter. The XRD results obtained for the Mg 58 Cu 31 Gd 11 are nearly identical to those for the Mg 65 Cu 25 Gd 10 , showing amorphous-like broad characteristic peaks. All the four characteristic temperatures, T g , T x , T m and T l , of the Mg 65 Cu 25 Gd 10 are essentially lower than those of Mg 58 Cu 31 Gd 11 , for both injection-cast rods and melt-spun ribbons. The glass forming abilities of the Mg 65 Cu 25 Gd 10 are similar to those of Mg 58 Cu 31 Gd 11 , for both injection-cast rods and melt-spun ribbons, indicated by T rg = 0.60 and γ = 0.42. The average microhardness of the Mg 65 Cu 25 Gd 10 is 2.41 GPa and 2.27 GPa for injection-cast bars and melt-spun ribbons, respectively, which are significantly lower than 2.84 GPa and 2.49 GPa of the Mg 58 Cu 31 Gd 11 . The nanohardness at the maximum load from the multiple loading is 3.5 GPa for Mg 65 Cu 25 Gd 10 , which is lower than 3.9 GPa for Mg 58 Cu 31 Gd 11 . The curves of load vs. the depth obtained from the nanoindentation tests all show stepwise behavior due to the pop-in events, and the step width increases as the indentation rate decreases. The modulus at the maximum load from the multiple loading obtained from the nanoindentation tests is 64.9 GPa for Mg 65 Cu 25 Gd 10 , which is lower than 70.7 GPa for Mg 58 Cu 31 Gd 11 . The fracture stress and strain of the Mg 65 Cu 25 Gd 10 BMG rod at room temperature are 490 MPa and 3%, respectively, smaller than those of the Mg 58 Cu 31 Gd 11 BMG rod, 548 MPa and 3.2%, respectively. The Mg 58 Cu 31 Gd 11 BMG rod is stronger at room temperature, and also shows higher yield stress and less deformable at elevated temperature, than the Mg 65 Cu 25 Gd 10 BMG rod.

The microstructure and performance of micro drills coated with Cr, Cr2N, and CrWCN thin films for applying to drill the PCB (printed circuit board) at high rpm (400 krpm) were systematically investigated by means of AFM, TEM, nano indentation and scratch test in this study. The results of properties evaluation for these coatings on the tungsten drill samples revealed that the doping of W accompanied with pursing C2H2 gas on the Cr2N coating effectively increases the hardness of Cr2N film from 8 GPa to 25 GPa and decreases the frictional coefficient from 0.35 to 0.25. In addition, when these three thin films were applied on the on-line test of drilling the PCB for 24,000 holes, the CrWCN thin film shows the best wear resistance among these three thin films, presenting the minimum flank wear and 4–5 times longer tool life than the uncoated samples. Therefore, the CrWCN thin film is suggested to be a prominent material for protective coatings according to its excellent wear resistance and adhesive capability.

Two sets of source target which consist of ZrCuAlNiV and ZrTiAlNiV, respectively were selected as the target materials for preparing a series of thin film coatings on the 304 stainless steel substrate by DC pulse magnetron sputtering process. The microstructures of these as-prepared ZrCuAlNiV and ZrTiAlNiV thin films were examined by X-ray diffraction and TEM observation. In parallel, the characteristic analysis of these ZrCuAlNiV and ZrTiAlNiV alloy thin films including surface roughness, and corrosion resistance were analyzed by atomic force microscopy (AFM), and tested by electrochemical method as well as salt spray testing, respectively. The results showed that the ZrCuAlNiV thin film exhibits a typical amorphous microstructure and smooth surface with average roughness about 1 nm. The ZrCuAlNiV thin film performs similar corrosion resistance to 304 stainless steel according to the result of salt spray testing in 5% NaCl solution. Additionally, the AC impedance value of ZrCuAlNiV is 20 times than 316L stainless steel and 4 times than ZrTiAlNiV, implying that the ZrCuAlNiV thin film has better corrosion resistance than the others owing to its amorphous state.

The amorphous alloy rods of (Zr53Cu30Ni9Al8)100−xSix (x = 0.25, 0.5, 0.75, 1) with a diameter of 2–6 mm were prepared by drop casting method in an Ar atmosphere. The thermal properties, including glass forming ability (GFA) and thermal stability during isothermal annealing of these amorphous alloys, and the mechanical properties have been systematic investigated by the combination of DSC, XRD, SEM, TEM, and compression test. The result of X-ray diffraction reveals that these entire (Zr53Cu30Ni9Al8)100−xSix alloy rods exhibit a typical amorphous diffraction pattern with only a broad maximum around 2θ around 40 degree. Both Tg (glass transition temperature) and Tx (crystallization temperature) of these (Zr53Cu30Ni9Al8)100−xSix alloys increase with the silicon addition. In addition, both the activation energy of crystallization and the incubation time of isothermal annealing these (Zr53Cu30Ni9Al8)100−xSix amorphous alloys indicate that the (Zr53Cu30Ni9Al8)99.25Si0.75 alloy possesses the best thermal stability in the (Zr53Cu30Ni9Al8)100−xSix alloy system. In parallel, the result of compression test shows that the yield strength increases with the addition of Si content and reaches to a maximum value about 1750 MPa with 3% plastic strain for the (Zr53Cu30Ni9Al8)99.25Si0.75 amorphous alloy.

The thermal plastic deformation behavior of the (Zr53Cu30Ni9Al8)99.5Si0.5 bulk metallic glass (BMG) was studied by means of thermo mechanical analysis (TMA) and high-temperature compression test in the supercooled liquid region. Using the result obtained from TMA, the deformation behavior for (Zr53Cu30Ni9Al8)99.5Si0.5 BMG rod was investigated by compression test at different strain rates (5 × 10−3∼5 × 10−1 s−1) and temperatures in the supercooled liquid region, specifically at 733 K, 738 K, 743 K, 748 K, and 753 K. The value of flow stress with a constant strain rate of 5 × 10−3 s−1 decreases with increasing temperature and reaches a relatively low flow stress of 36 MPa at the test temperature of 753 K. Conversely, the value of flow stress increases with the strain rate in compression. In this paper, an imprinted hologram pattern with 0.6 μm depth was demonstrated which showed extremely good microforming ability of this (Zr53Cu30Ni9Al8)99.5Si0.5 BMG in the supercooled liquid region.

The Au based amorphous micro-pillars are fabricated by using focus ion beam (FIB) and tested in micro-compression at ambient and elevated temperatures from 300 to 408 K. The room temperature strength of current micro-pillars could reach to 1600-2000 MPa, much higher than the measured strengths for the 3 mm bulk compression specimen. The stress increment can be rationalized by the Weibull statistics. The current Au based micro-pillars maintain inhomogeneous deformation with one (at most two) principal shear band from 300 up to 393 K. At or above T g (403 and 408 K), the micro-pillars are deformed in a homogeneous manner without the trace of any shear band. For micro-forming, it should be born in mind that there would be apparent stress increment while forming micro- or nano-scaled patterns and pieces.

The thermomechanical properties and viscous flow behaviors of the Mg 65 Cu 25-x Ag x Gd 10 (x = 0, 3, 10at%, namely, Mg 65 Cu 25 Gd 10 , Mg 65 Cu 22 Ag 3 Gd 10 , and Mg 65 Cu 15 Ag 10 Gd 10 ) bulk metallic glasses in the supercooled viscous region under the loading condition were investigated using the thermomechanical analyzer. In this study, the supercooled viscous temperature windows, the minimum viscosity, the fragility parameter, and the deformability parameter would all be degraded with increasing Ag addition, leading to the negative factors for the micro-forming and nano-imprinting practices. The base Mg 65 Cu 25 Gd 10 alloy appears to be more promising than the Ag containing alloys when the viscous forming is under consideration.

Mg65Cu20Y10Ag5 Amorphous/ nano ZrO2 composites alloy powder were fabricated through the combination method of melt spinning and mechanical alloying (MA). The melt spun amorphous matrix ribbons are ground into powders and mixed with 3 vol.% ZrO2 nano particles in the planetary mill. After then formed by hot pressing in Ar atmosphere under the pressure of 700 MPa at the temperature of soft point which measured by TMA (Thermal mechanical Analysis). The hot-pressed bulk composite specimens are compression tested at different temperature within the supercooled temperature region. The flow stress was found decrease with increasing temperature dramatically when the temperature exceeds the middle temperature of supercooled region. The specimens after compression test were examined by X-ray diffractometry and SEM to investigate its crystallinity and fracture mechanism.

The (Cu42Zr42Al8Ag8)100-xSix amorphous alloy rods, x =0 to 1, with 3 mm in diameter were prepared by Cu-mold drop casting method. The glass forming ability, thermal properties and microstructure evolution was studied by differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). The XRD result reveals that these as-quenched (Cu42Zr42Al8Ag8)100-xSix alloy rods exhibit a broaden diffraction pattern of amorphous phase. The crystallization temperature and GFA (glass forming ability) of (Cu42Zr42Al8Ag8)100-xSix alloys increase with the silicon additions. The highest Trg (0.59) and γ value (0.405) occurred at the (Cu42Zr42Al8Ag8)99.75Si0.25 and (Cu42Zr42Al8Ag8)99.5Si0.5 alloy. In addition, both of the activation energy of crystallization and the incubation time of isothermal annealing for these (Cu42Zr42Al8Ag8)100-xSix alloys indicates that the (Cu42Zr42Al8Ag8)99.25Si0.75 alloy posses the best thermal stability among the (Cu42Zr42Al8Ag8)100-xSix alloy system.

The results of atmosphere-controlled tensile test in various conditions (with different strain rate at different temperature under vacuum, air, or water vapor atmosphere) revealed that the addition of boron and chromium would improve the elongation as well as ultimate tensile strength (UTS) of the Ni-19Si-3Nb based alloys over a wide range of temperature under air and water vapor atmosphere. The UTS and elongation can reach to 1270 MPa and 14%, respectively at 873K in each kind of atmosphere. On contrary, the alloy without boron addition only presents ductile mechanical behavior in vacuum. This is evident that boron and Cr elements present positive effect on suppressing the environmental embrittlement in air and water vapor atmosphere from room temperature to 1073 K for the Ni-19Si-3Nb base alloy. In addition, both of UTS and elongation present quite insensitive on the strain rate when test at the temperature below 973 K. However, the UTS exhibits very dependent on the strain rate when test temperature above 973 K, decreasing the ultimate tensile strength with decreasing strain rate.

The preparation of Mg 49 Y 15 Cu 36 metallic glass powders was accomplished by mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these Mg 49 Y 15 Cu 36 amorphous powders was investigated by differential scanning calorimeter (DSC). The T g , T x and Δ T x are 450, 492, and 42 K, respectively. The as-milled Mg 49 Y 15 Cu 36 powders were then consolidated by vacuum hot pressing into disc compacts with a diameter and thickness of 10 and 1 mm, respectively. After vacuum hot pressing, bulk Mg 49 Y 15 Cu 36 metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix was obtained. The applied pressure during consolidation can enhance the thermal stability and prolong the existence of amorphous phase inside Mg 49 Y 15 Cu 36 powders.

Recently, the high performance W–Ni–Fe–Co heavy tungsten alloy has become as the major core material of armor piercing ammunition. Since the melting temperature of tungsten element is too high to be fabricated by the melting process, that the W–Ni–Fe–Co alloy only can be synthesized by powder metallurgy process. In this study, two compositions of alloy powders, 93W–3Ni–2Fe–2Co and 93W–3.5Ni–1.5Fe–2Co, were selected for investigating their microstructure and mechanical properties after solid-phase sintering. These pre-alloyed powders with crystal cell size about 16 nm were synthesized by mechanical alloying (MA) the mixture of appropriate composition of pure elements in the Spex mill for 8 h. Then, the MA powders were compressed by cold isostatic pressing (CIP) and vacuum sintered at various temperature below 1400 °C for different time. Microstructure characterization of the sintered tungsten heavy alloys was conducted by means of SEM with EDS capability, X-ray diffraction (XRD), and TEM techniques. The result reveals that the microstructure of these sintered alloys was found to consist of the tungsten matrix phase and the Fe–Ni solid solution phase. The hardness of these sintered tungsten heavy alloy presents a trend with increasing sintering temperature and sintering time.

The effect of strain rate and environment on the mechanical behavior at different temperatures of the Ni–19Si–3Nb–0.15B–0.1C alloy is investigated by atmosphere-controlled tensile testing under various conditions at different strain rates and different temperatures). The results reveal that the Ni–19Si–3Nb–0.15B–0.1C alloy exhibits ductile mechanical behavior (UTS ∼ 1250 MPa, e ~ 14%) at temperatures below 873 K under different atmosphere conditions. However, the alloy without boron and carbon addition shows ductile mechanical behavior only when the sample is tested in vacuum. This indicates that the microalloying of boron and carbon does overcome the environmental embrittlement from water vapor at test temperatures below 873 K for the Ni–19Si–3Nb base alloy. However, the boron and carbon doped alloy still suffers from embrittlement associated with oxygen at a medium high temperature (i.e. 973 K). In parallel, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 873 K. However, the ultimate tensile strength exhibits high dependence on the strain rate in air at temperatures above 873 K, decreasing the ultimate tensile strength with decreasing strain rate.

The Mg65Cu25Gd10-xNdx (x=0 ~ 10) amorphous alloy rods with 3~6 mm in diameter were prepared by Cu-mold injection method. The thermal properties and mechanical properties of these amorphous alloys have been investigated by DSC, SEM with EDS capability, X-ray diffractometry (XRD) and Vickers hardness test. The XRD revealed that these entire as-quenched Mg65Cu25Gd10-xNdx alloy rods exhibit a broaden diffraction pattern of amorphous phase. A clear Tg (glass transition temperature) and supercooled region (about 30~60 K) were revealed for all of those Mg65Cu25Gd10-xNdx alloys. In addition, the single stage crystallization of the Mg65Cu25Gd10 alloy was found to change into two stages crystallization when the Nd element was added into this alloy. In parallel, the crystallization temperature (Tx) and supercooled region (Tx) presents a decreasing trend with increasing Nd content. The lowest liquidus temperature (Tl, about 721 K) occurs at the Mg65Cu25Gd8Nd2 alloy. In addition, The Mg65Cu25Gd8Nd2 alloy exhibits the high γ value (0.416, defined as γ= Tx/Tg+Tl), a relatively high Trg (0.59, defined as Trg = Tg/Tl) and the highest hardness in these alloys.

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Pb1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Pb1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 760 K and 850 K, respectively. The supercooled liquid region is 90 K. The appearance of wide supercooled liquid region may be mainly due to the Pb additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Pb1 powders.

The thermal and mechanical characteristics of various Mg-Cu(Ni)-Y(Gd) metallic glassy alloys prepared by melt spinning are examined using differential scanning calorimetry (DSC), thermomechanical analyzer (TMA), and instrumental nanoindenter. The replacement of Y by Gd appears to benefit both the thermal and mechanical properties, while the replacement of Cu by Ni improves only the hardness and modulus, with the sacrifice of thermal characteristics. The amorphous Mg-Cu-Gd based alloys can be fabricated into rods with a diameter greater than 6 mm, with minimum porosity and reasonable toughness.

There have been many alloy systems for the Mg based bulk metallic glasses (BMGs), with the previous optimum composition being Mg65Cu25Y10. In this study, new optimum alloy designs are made based on the theoretical model involving the electron per atom e=a-related criterion and the recent model of optimum composition extension from the binary eutectic-pair criterion. Both models suggest that the optimum Mg based BMGs might possess a composition with a lower amount of Mg element. It follows that a series of Mg based BMGs with 50–65 at% Mg and 10–25 at% rare earth element are prepared. The glass forming ability, thermal characteristics, and mechanical performance are examined and discussed. [doi:10.2320/matertrans.MJ200724]

Both the glass forming ability and thermal stability of the Zr 65-x-y Al 7.5 Cu 17 Ni 10 amorphous alloy can be improved by the appropriate addition of Si and B. The metalloid elements would extend the nucleation stage and result in more small crystalline particles. The basic crystallization kinetics for the Si/B containing alloys is still similar to the base alloy, but would proceed at a higher temperature or a more sluggish speed.

Amorphous Mg65Cu20Y10Ag5/nano ZrO2 composite alloys are fabricated through mechanical alloying (MA) in the planetary mill, using amorphous matrix alloy prepared by melt spun and 3 vol% spherical nano-sized ZrO2 particles. The specimens were hot pressed in Ar atmosphere under the pressure of 700 MPa at the temperature of soft point which is determined by TMA (Thermo mechanical Analysis). The hot-pressed composite alloy can reach to a 96% density, the hardness of 315 � 10 in Hv scale, and the compressive strength of 690 MPa. In addition, the result of mechanical test revealed that the nano-sized ZrO2 dispersion can obviously increase hardness as well as toughness of the Mg based amorphous alloy. Moreover, after compression test at 426 K (sample has been deformed 60 vol%), the hardness of hot-pressed composite alloy dramatically increases to Hv 400 � 25. An image of shear band being stopped in front of the ZrO2 particle was found by the TEM observation. Base on these two evidences, suggests that the strength of amorphous Mg65Y10Cu20Ag5 with 3 vol% ZrO2 composite alloy could be potentially improved by healing its residue porosity with hot deformation method within the supercooled liquid temperature region.

The Mg 58 Cu 31 Y 11-x Nd x (x = 0 ∼ 11) amorphous alloy rods with 3∼10 mm in diameter were prepared by Cu-mold injection method. The XRD result reveals that these entire Mg 58 Cu 31 Y 11-x Nd x alloy rods exhibit a broaden diffraction pattern of amorphous phase. A clear Tg (glass transition temperature) and supercooled region (about 70 K) were revealed for all of those Mg 58 Cu 31 Y 11-x Nd x amorphous alloy rods. The single stage crystallization of the Mg 58 Cu 31 Y 11 alloy was found to change into two stages crystallization when large amount of Nd element was added into this alloy. In parallel, the crystallization temperature (T x ) and supercooled region (ΔT x ) present a decreasing trend with increasing Nd content. The highest y value of 0.414 occurs at the alloy compositions of Mg 58 Cu 31 Y 4 Nd 7 and Mg 58 Cu 31 Y 6 Nd 5 in this alloy system. Therefore, suitable addition of Nd element can obviously increase the glass forming ability for the Mg 58 Cu 31 Y 11-x Nd x alloy system.