Based Bulk Metallic Glasses Research Articles

Tailoring the glass forming ability, mechanical properties and corrosion resistance of Cu–Zr–Al bulk metallic glasses by yttrium addition

The effect of yttrium (Y) on the glass-forming ability (GFA), mechanical properties and corrosion of (Cu50Zr43Al7)100-xYx (x = 0, 2 and 4, in at. %) alloys was investigated. The GFA of Cu50Zr43Al7 alloy was improved by the addition of Y, with a GFA of 15 mm in diameter being obtained for (Cu50Zr43Al7)98Y2. In uniaxial compression, the bulk metallic glasses (BMGs) exhibited a limited plastic strain of less than 1%, however compressive fracture strength and Young's modulus of 1787–2006 MPa and 101–122 GPa were achieved, respectively. Fracture surfaces and shear bands were studied via scanning electron microscopy. The corrosion behavior of BMGs was analyzed by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS) in acidic chloride (1 M HCl) and neutral chloride (0.6 M NaCl) environments. As a result of the Y addition, the corrosion resistance of the base BMG was improved.

Effect of fictive temperature on tribological properties of Zr44Ti11Cu10Ni10Be25 bulk metallic glasses

Zirconium (Zr) based bulk metallic glasses (BMGs) have emerged as a potential material for various engineering applications due to their unique and tunable mechanical properties. Heat treatment of the BMGs plays a vital role in changing the mechanical as well as tribological properties. In the present work, the effect of the fictive temperature (Tf) on the mechanical and tribological behavior of Zr based BMGs with a glass transition temperature (Tg) of 352 °C has been studied by nanoindentation and micro-scratch testing at constant (load 10 N) and progressive (0.5–25 N) loading conditions. The BMGs were heat treated at three different fictive temperatures ranging from 0.91Tg (320 °C) to 1.05Tg (370 °C). Hardness and effective elastic modulus were observed to be highest (8.3 GPa and 128 GPa, respectively) for the metallic glass with a fictive temperature of 0.91Tg (320 °C). With an increase in fictive temperature, hardness and effective elastic modulus decrease due to decreased short-range ordering and more free volume (density fluctuations) in the internal structure, which enhances atomic and plastic flow in the material. For constant loading, wear resistance is observed to be similar for as-cast BMG and BMG with Tf = 1.05Tg, but increases by 65% and 40% from as-cast to BMGs with Tf's of 0.91Tg and 0.99Tg, respectively. For progressive loading, the wear resistance increases by 10% from as-cast to 0.91Tg, whereas it decreases by 75% and 76% as Tf increases to 0.99Tg and 1.05Tg, respectively. BMGs with Tf = 0.91Tg are observed to be the most wear resistant in both the loading conditions, making it a viable candidate for biomedical applications, machine tools, and engine parts where wear resistance of the component during service is a dominating factor.

Minor alloying upon non-isothermal crystallization kinetics of a Cu-based bulk metallic glass: a comparative investigation

This paper reported the alloying effects in the non-isothermal crystallization of as-cast bulk metallic glasses. Three kinds of Al, Ni and Si elements with minor quantity of 0.5 at% were individually added into a base Cu55Zr37Ti8 bulk metallic glass. Differential scanning calorimetry was utilized to characterize the crystalline processes during heating, and Johnson–Mehl–Avrami equation was adopted to determine and evaluate the crystallization kinetic parameters. The results disclose that alloying processing with 0.5 at% of Al, Ni and Si elements altered the crystallization kinetic behaviors. Alloying with 0.5 at% of Ni performs more remarkable constraint on the nucleation and growth of the crystallization with regard to alloying with the same quantity of Al and Si elements in the base bulk metallic glass and favors the suppression of crystallization.

Fracture response of [formula omitted] bulk metallic glass subjected to quasi-static compression loading

Lanthanum based bulk metallic glass (BMG) is one of the BMG which have the excellent glass-forming ability (GFA). In this empirical study, as-received La61.4Al15.9Ni11.35Cu11.35 bulk metallic glasses were subjected to a quasi-static compression test. The results show the maximum modulus Young’s of 191 GPa, the compressive force of 590 MPa and the compressive displacement at maximum force of 0.35 mm. The La-based BMG were comparable to the 304 stainless steels in term of the mechanical properties. The La-based BMG fracture response from the quasi-static compression test was documented. The fracture response under compressive loading is vital to understand the La-based BMG for the promising used in lightweight alloy applications.

Theoretical prediction and experimental evaluation of glass forming ability, density and equilibrium point of Ta based bulk metallic glass alloys

The present investigation aims at evaluating the Glass Forming Ability (GFA), density (ρ) and equilibrium melting point (T0) of Ta(W/Hf)-Ni-B based bulk metallic glass (BMG) alloy system. Initially, the theoretical GFA, based on thermodynamic parameters PHSS, ρth, based on rule of mixture of volume and T0th, using Thermo-cal software for all alloy systems have been calculated and then mapped in Ta-Ni-B, Ta(W)-Ni-B and Ta(Hf)-Ni-B diagrams respectively. Maps for individual alloy system were then superimposed based on high GFA (< −5 kJ/mol), high density (>13 g/cc) and low melting point (<1400 °C). A series of compositions of ternary TaxNiyBz, (where x = 46, 47, y = 44, 45 and z = 8, 9, 10 at.%) and quaternary Ta50Ni(49.5-u)WuB0.5, (where u = 1, 2, 3, 5 at.%) and Ta(50-v)Ni(50-w)Hf(v+w-0.5)B0.5 (where v = 7, 9 and w = 8,10 at.%) alloys have been selected based on the intersections of overlapped PHSS, ρth and T0th regions in respective superimposed diagrams and subsequently considered for conducting experiments for validation. All these alloys of selected compositions were first cast from elemental mixture, followed by processing through rapid solidification route to produce ribbons and characterizing for structural and thermal analyses. It reveals that crystalline phases exist along with amorphous phase in TaxNiyBz alloys, whereas completely amorphous phase can be observed in quaternary Ta50Ni(49.5-u)WuB0.5, and Ta(50-v)Ni(50-w)Hf(v+w-0.5)B0.5 alloy systems. B has detrimental effect for the formation of glassy phase, whereas W bearing Ta-Ni-B alloys have higher GFA as compared to that of Hf bearing Ta-Ni-B alloys. The experimental results are also corroborated with the theoretical prediction.

Preparation of non-magnetic and ductile Co-based bulk metallic glasses with high GFA and hardness

Co(Fe,Ni)-based bulk metallic glasses (BMGs) characterized with super-high hardness and strength are generally brittle and strong magnetic, significantly undercutting their momentous applications as coating materials. Here we report Co92-xNi2Ta6Bx (x = 29–35) non-magnetic BMGs with a combination of appropriate plasticity and GFA, as well as superhigh hardness and strength. BMG Rods with maximum diameters up to 2.5 mm were fabricated by copper mold casting method. All alloys exhibit superhigh compressive fracture strength of 5.21–5.63 GPa, high hardness of 1290–1410 HV and plasticity of 1.2–3.5%. Besides, the amorphization can effectively decrease the magnetization and all the alloys show non-magnetic properties at glassy state. The partial crystallization in the high B content glassy alloys will not significantly change the non-magnetic or poor-magnetic feature. It is also found that the increase of B content can substantially improve the thermal stability of the glassy alloys and inhibit the formation of strong magnetic phases. These Co-based alloys are promising candidates for the future application of spray coating materials.

High Temperature Deformation Behavior of High Strength and Toughness Ti-Ni Base Bulk Metallic Glass Composites

High Temperature Deformation Behavior of High Strength and Toughness Ti-Ni Base Bulk Metallic Glass Composites

Enhanced glass forming ability, mechanical, and magnetic properties of Fe41Co7Cr15Mo14Y2C15B6 bulk metallic glass with minor addition of Cu

In this study, enhancement of glass forming ability (GFA) as well as mechanical and magnetic properties of a Fe-based bulk metallic glass (BMG) was investigated with minor addition of Cu. The obtained results revealed that appropriate addition of Cu could significantly improve GFA of the base BMG. Furthermore, the mechanical properties of the investigated BMG were improved by the addition of 25 at.% Cu due to the positive heat of mixing between Cu and Fe atoms, decreasing the free volume and density of porosities. Therefore, the relatively good and comprehensive properties of the BMG containing 0.25 at.% Cu were exhibited; also, as a result of an excellent combination of good GFA (ΔTx = 48 K), microhardness (1425 HV), failure strain (εf = 2.1%), and failure strength (σf = 4400 MPa) was created it as a promising candidate for engineering applications. Furthermore, the magnetic measurements revealed that ferromagnetic properties of this Fe-based BMG decreased with the addition of 0.25 at.% Cu, but increased significantly with the addition of 0.5 at.% Cu.

Structural modifications in sub-Tg annealed CuZr-based metallic glass

Short term sub-glass transition annealing controls the structural reordering and nanocrystallization of CuZr−based bulk metallic glasses (BMGs). Using this method, 5 times higher resistance against strain softening as confirmed by three-point bending tests is attained. Homogenously dispersed nanoparticles in sizes of 20–50nm accounts for the remarkable shifts and peak formations on reciprocal space together with the diffraction spots observed on 2D diffraction pattern. Real-space pair distribution function analysis reveals noticeable changes in peak shapes and positions correlated with the changes in short- to medium-range ordering. The differences in the partial nearest neighbor numbers upon annealing mark the dominant Zr−Zr pair to diminish whereas the Cu−Cu pair becomes prominent, hinting that Cu diffusion is mainly responsible for structural reordering and formation of new phases. The pursued study using hard X-ray synchrotron radiation reveals important aspects of structural changes preceding nanocrystallization, which in turn enhances the mechanical performance in BMGs.

Memory phenomenon in a lanthanum based bulk metallic glass

In this paper, we experimentally investigate two memory phenomena in a lanthanum based bulk metallic glass (BMG). While the temperature memory effect (TME) is not found by differential scanning calorimeter (DSC) test, shape recovery is observed in samples indented at both low and high temperatures. In terms of shape memory related characteristics, this BMG shares some features of shape memory alloys (SMAs) due to its metal nature, and some other features of shape memory polymers (SMPs) owing to its glassy–rubbery transition. The formation of protrusion in the polished sample after heating to super-cooled liquid region (SCLR) indicates that surface tension is not a necessarily positive contributor for shape recovery. Release of internal elastic stress is concluded as the major player. Although the amorphous nature of BMGs enables for storing appreciable amount of internal elastic stress upon deformation, without the presence of cross-linker as in typical SMPs, the shape recovery in BMGs is rather limited.

Scratch induced deformation behavior of hafnium based bulk metallic glass at multiple load scales

The scratch induced deformation behavior of Hafnium based bulk metallic glass (BMG) at micro- and macro-load scales is reported in this study. The micro-scratch deals with a normal load range of 1000–8000μN, whereas the macro-scale scratches are made with a normal load reaching up to 5N. Increase in the load beyond 2000μN changes the deformation mechanism from plowing to fracture and chipping. The plastic strain is mostly accommodated by shear band formation with a significant amount of free volume generation. A change in the strain rate helps in the nucleation of shear bands and prevents fracture and chipping in the case of micro-scratches made at ramp loading as compared to constant load. Higher strain rate and heat generation in the track causes increased strain hardening in macro-scratch, which could be attributed to increased probability of nano-crystallization. Complex shear band structure is evolved during scratching, which is attributed to the mixed type of loading, consisting of compressive normal load and lateral shear load across scratch-track.

Sample Preparation and HR-TEM Investigation Techniques of Ti Based, Ga Containing, Amorphous Alloys

Titanium based bulk metallic glasses (BMGs) are characterized by properties such as high corrosion resistance, Youngs modulus, hardness, fracture strength and wear resistance that recommend them as performant biomaterials for orthopedics and dentistry. Present researches have been focused on some Ti-Zr-Cu-Ga-Si-Sn alloy which could be feasible alternative to almost classical nickel containing BMGs. has been casted by vacuum suction in a copper mold. Suction casting has been used to produce by mean of ultra-rapid cooling experimental samples as 2mm cylinders, and complex investigation program based on optical microscopy, SEM, and HR-TEM techniques has been performed to characterize resulting microstructure. Although presence of gallium produces considerable difficulties in sample preparation, investigations based on high resolution transmission electron microscopy (HR-TEM) have evidenced simultaneous presence of amorphous, crystalline and partially crystalline structures.

Deformation feature and properties of Zr based bulk metallic glass treated by laser shock peening

Laser shock peening is promising surface treatment technique to improve the mechanical properties of metals material through introducing a deep compressive residual stresses region. In this work, LSP was employed to treat Zr based bulk metallic glasses (BMGs). In contrast to the work softening in BMGs, laser shock peened BMG shows significant hardening in the plastic deformed region. Furthermore, the plastic deformation region exhibits unique deformation features, which is dependent on the thickness of the samples. The deformation morphology under the impacted region was also studied. The mechanism for the hardening and formation of unique deformation features is discussed.

The atomic-scale mechanism for the enhanced glass-forming-ability of a Cu-Zr based bulk metallic glass with minor element additions.

It is known that the glass forming-ability (GFA) of bulk metallic glasses (BMGs) can be greatly enhanced via minor element additions. However, direct evidence has been lacking to reveal its structural origin despite different theories hitherto proposed. Through the high-resolution transmission-electron-microscopy (HRTEM) analysis, here we show that the content of local crystal-like orders increases significantly in a Cu-Zr-Al BMG after a 2-at% Y addition. Contrasting the previous studies, our current results indicate that the formation of crystal-like order at the atomic scale plays an important role in enhancing the GFA of the Cu-Zr-Al base BMG.

Surface Texture and Elemental Characterization of High Aspect Ratio Blind Micro Holes on Different Materials in Micro EDM

Micro features machined through micro electrical discharge machining (micro EDM) are adversely affected by tool wear. Tool electrode and machined parts are deformed due to stochastic behaviour of discharge processes. Deposition of tool electrode material on workpiece deteriorates the surface quality of the micro part. Study of the surface quality of blind micro hole is very difficult in non-destructive method due to its miniature size. In this communication, attempts have been made to study the surface quality of high aspect ratio blind micro holes by opening the holes in destructive method. High aspect ratio blind micro holes were drilled in wear resistant high grade steel (block gauge material), zirconium based bulk metallic glass (BMG) Vit 1, titanium super alloy Ti-6Al-4V, oxygen free high thermal conductivity (OFHC) copper, Monel 400 and hard anodized aluminium alloy 6082 T6 in micro EDM by cylindrical tungsten (W) electrode and opened the holes axially through wire EDM (WEDM) to study the surface texture of the opened holes using 3D optical profilometry technique. Elemental analysis of materials of tips of tool electrode and surfaces of the opened micro holes were studied by using energy dispersive X-ray spectroscopy (EDS) technique in scanning electron microscope (SEM). Deformations of tool electrode and tool profile on the workpiece were also studied.

Solidification processes in Cu–Zr–Ag amorphisable alloy system

Abstract The Cu–Zr–Ag system is one of Cu−Zr based bulk metallic glasses (BMG) that has been in the center of great interest for a long time. This work summarizes results on solidification in the Cu–Zr–Ag ternary alloys and relationship between the cooling rate and their microstructure. The alloys in a wide range of compositions were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques. The surface of stable liquidus miscibility gap has been presented by isothermal sections in this system. The central part of liquidus projection of the ternary Cu–Zr–Ag system is determined based on the harmonization of experimental results and the calculated phase diagrams. Due to the liquid separation, amorphous/crystalline composites could be obtained with a silver content up to 50 at%. The primary solidified phases were identified in different samples cooled with a controlled cooling rate (5 K/min), in the arc melting furnace (master alloys) and in a wedge shape mould. It has been shown that the m-phase (or AgCu 4 Zr) has the lowest and the (CuAg) 10 Zr 7 the highest driving force for nucleation in this system. It has been shown that the glass forming ability depends not only on the properties of atomic constituent but on the phases formed during the solidification of undercooled liquid.

Electron beam brazing of Zr62Al13Ni7Cu18 bulk metallic glass with Ti metal

Electron beam brazing (EBB) of 2 mm thick Zr62Al13Ni7Cu18 bulk metallic glass (BMG) plate to Ti metal has successfully been accomplished by employing optimized electron beam brazing parameters and providing high cooling rate during solidification. The beam was irradiated 0.3 mm on the BMG side from the interface to avoid significant change in the chemical composition of weld metal in comparison to the base BMG. The welded joint was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray radiography techniques. The welded joint was found to be very sound with no crystallization or defects around the interface. Finally, microhardness profile across the welded joint was determined indicating a little increase in the hardness of the weld metal in comparison to that of BMG.

Development of Fe-B Based Bulk Metallic Glasses: Morphology of Residual Phases in Fe50Ni16Mo6B18Zr10 Glass

Iron-boron based bulk metallic glasses (BMG) development has been initiated using Fe40Ni38Mo4B18 as precursor. Addition of zirconium up to 10 atomic % along with the reduction of Ni proportion improves the glass forming ability (GFA), which is optimum when Ni is suppressed in the alloy. However melting instability occurred during the materials fabrication resulting in the formation of residual crystalline phases closely related to the amorphous phase. Microstructure study shows an evolution from amorphous structure to peculiar acicular structure, particularly for Fe50Ni16Mo6B18Zr10, suggesting the amorphous structure as interconnected atomic sheets like “atomic mille feuilles” whose growth affects the alloys’ GFA.

Mechanics of Ti-Ni BMG-Based Alloys: Experimental Study

Titanium-nickel(Ti-Ni)-basedbulkmetallicglass(BMG)alloyswerepreparedbycentrifugalcastingintoacoppermold.Theeffect of five rolled temperatures, namely, room temperature and 200, 300, 400, and 500C, on the behavior of amorphous BMG, the microstructural features, and the mechanical properties were investigated. High-resolution scanning electron microscopy (HRSEM) reveals the formation of nanoparticles in the amorphous alloys. The ultimate compressive stress of the rods rolled at 300C was found to be the highest, whereas that of

EFFECTS OF THE ADDITION OF Ti OR Al ON THE WETTING BEHAVIORS AND INTERFACIAL CHARACTERISTICS OF Zr 50 Cu 50 BULK METALLIC GLASS/W SUBSTRATE

In order to get the good performance of metal W reinforced Zr–based bulk metallic glass (BMG) matrix composites, it is necessary to understand the effects of alloy elements on the wettability between Zr–based BMG and W substrate. In this work, the effects of the addition of Ti or Al on the wetting behaviors and interfacial characteristics of Zr50Cu50 BMG on W substrate were studied at different temperatures in a high vacuum by using a sessile drop technique. The SEM and XRD were used to analyze the microstructure and bonding mechanism of the Zr50Cu50 BMG / W * <tRtdAr/oVO 2011CB606301, <td6Amd O 50825402 j` Z l ~d O 20111019 bX s <,< : 2012–10–27, s f',< : 2012–12–24 k8{ : n< , , 1979 V, l DOI: 10.3724/SP.J.1037.2012.00643