Supercooled Liquid Region Research Articles

Oxide-Metal Hybrid Glass Nanomembranes with Exceptional Thermal Stability.

Contrary to oxide or polymeric glasses, metallic glasses are infamously known for their relatively limited thermal stability, which is often characterized by their narrow supercooled liquid regions. Nonetheless, we successfully fabricated metallic-glass based nanomembranes with an ultrahigh thermal ability by a polymer surface buckling enabled exfoliation technique. These nanomembranes exhibit a distinctive nanostructure with nanosized metallic-glasses encapsulated within an interconnected nanoamorphous-oxide network. Due to a pronounced nanoconfinement effect, crystallization is significantly suppressed. Consequently, these oxidized metallic-glass nanomembranes initiate a glass transition at 324 K at a heating rate of 10 K/min. Remarkably, they also showcase an expansive supercooled liquid region of 448 K, surpassing various metallic and oxide glasses reported. Furthermore, these nanomembranes not only exhibit a low elastic modulus but also achieve superplasticity even at room temperature. This unique blend of thermomechanical properties positions our metallic-glass based nanomembranes as an ideal candidate for nanofabrication processing, such as nanoimprinting, for the creation of next-generation nanodevices.

Enhancements of magnetic properties and compacted density for Fe-based amorphous soft magnetic composites via hot compacting under an ultra-low pressure

Amorphous FeSiBCCr soft magnetic composites (FeSiBCCr-SMCs) with high compacted density (ρc) and excellent magnetic properties has been successfully hot-compacted under an ultra-low pressure of 160 MPa. The thermoplastic deformation of amorphous powders within the supercooled liquid region can give rise to the increase of ρc and the reduction of non-magnetic pores fraction for the SMCs. This situation is conductive to the decrease in resistance of domain wall motion during magnetization process of SMCs, and finally contributes to the improvement of SMCs’ soft magnetic properties. Under the recommended conditions with the compaction temperature (Tc) of 475 ℃, the pressure holding time (th) of 6 min, and the molding pressure (Pm) of 160 MPa, the FeSiBCCr-SMCs’ ρc increases by 28.8 % to 6.53 g/cm3, the corresponding effective permeability (μe) increases by 3.39 times to 73.1, while its total core loss (Pcv) reduces by 57.4 % to 275.3 kW/m3 at 100 kHz, 0.05 T compared with those of the SMCs prepared at Pm=600 MPa, Tc=25 ℃.

Fe-based amorphous soft magnetic composites with excellent magnetic properties fabricated via low-pressure hot compacting

FePBNbCr amorphous soft magnetic composites (SMCs) with high compaction density (ρc) and commendable magnetic properties were successfully fabricated via low-pressure hot-compacting at 160 MPa. Due to the thermoplastic properties of amorphous powders in supercooled liquid region (ΔTx), the hot-compacting in the ΔTx is conducive to the increase of ρc for the amorphous SMCs, thereby improving the corresponding soft magnetic properties via reducing the number of pinning sites. Compared with these of the cold-compacted amorphous SMCs at 600 MPa, the ρc increases by 20.3 % to 6.04 g/cm3, the effective permeability increases by 5.26 times to 95.3, while the corresponding total core loss decreases 74.5 % to 154.4 kW/m3 (100 kHz, 0.05 T) for the amorphous SMCs hot-compacted at 495 °C with a pressure holding time of 6 min. These results indicate that the low-pressure hot compacting is an effective measure to further improve soft magnetic properties of the amorphous SMCs for rapidly adapting to the development needs of high-frequency and miniaturization of electronic devices.

The rheological behavior of brittle BMGs of Cu44.25Ag14.75Zr36Ti5 and Ti32.8Zr30.2Cu9Ni5.3Be22.7 in the supercooled liquid region

Bulk metallic glasses (BMGs) show limited plasticity at room temperature. However, BMGs usually exhibit superplasticity and high plastic forming ability in their supercooled liquid region (SLR). The rheological behavior of BMGs in SLR is vitally important to their thermoplastic forming process. In contrast to the ductile BMGs, thermoplastic deformation behavior of brittle BMGs is rarely reported. In present work, the rheological behavior of two brittle BMGs with high glass forming ability Cu44.25Ag14.75Zr36Ti5 and Ti32.8Zr30.2Cu9Ni5.3Be22.7 was investigated on Gleeble3500. The two BMGs can deform homogeneously depending on the temperature and strain rate. According to the high value of m (strain rate sensitivity index), which is the most important mechanical characteristic of a superplastic material, the two BMGs show superplasticity in their SLR with m ≥ 0.3. Based on the free volume model, their activation volumes are calculated as 0.263∼0.486 nm3 and 1.261∼1.650 nm3, indicating the minimum displacement clusters with average 26∼48 and 91∼127 atoms, for Cu44.25Ag14.75Zr36Ti5 and Ti32.8Zr30.2Cu9Ni5.3Be22.7, respectively. Thus, the two investigated brittle BMGs can be thermoplastic processed in the SLR and the deformation maps are given. BMG Cu44.25Ag14.75Zr36Ti5 shows better machinable property than Ti32.8Zr30.2Cu9Ni5.3Be22.7. Compared to the ductile BMGs, no Newtonian flow is found for the two investigated brittle BMGs.

Compositional dependence of glass-forming ability, mechanical and magnetic properties of Ce-Ni-Al (Ga) alloys

The glass-forming ability, mechanical and magnetic properties of Ce60Ni25Al15-xGax (x=0, 4, 8 and 15) melt-spun alloys have been investigated. All the alloys show the formation of glassy phase. The supercooled liquid region increases with increase in Ga addition and becomes maximum for x=15 indicating its better glass-forming ability for this composition. A new metallic glass (MG) composition Ce60Ni25Ga15 has been found upon complete substitution of Al by Ga. The mechanical behavior of these alloys has been studied by determining various indentation parameters such as micro-hardness, yield strength and Meyer’s exponent. The microhardness property of the Ce-Ni-Al alloy is improved by the addition of Ga. The difference in the formation of shear bands for x=0 and 15 alloys are discussed by estimating the pile-up parameter. The magnetization (M-H) curves of all the samples at 5 K show paramagnetic characteristics with no magnetic hysteresis. The findings reveal that the concentration of Ga has a significant impact on the properties of these alloys.

Kinetics study and fragility of (Cu50Zr43Al7)98Y2 bulk metallic glass

Crystallization transformation kinetics and fragility of (Cu50Zr43Al7)98Y2 bulk metallic glass (BMG) were investigated at non-isothermal and isothermal conditions by differential scanning calorimetry. Activation energies for the BMG were calculated for the glass transition, onset crystallization, and crystallization peak using various methods of non-isothermal analysis. Results suggested that atomic rearrangement during glass transition is more complex than crystallization, and growth poses greater challenges than nucleation. Isothermal analysis conducted in the supercooled liquid region provides evidence of crystallization being controlled by diffusion, with a calculated mean Avrami exponent of 2.2. Additionally, the findings of fragility studies and kinetic studies demonstrated a strong correlation with the glass-forming ability (GFA), thereby validating the high GFA of the BMG analyzed in this study. Thus, this research results provide a detailed understanding of the complex crystallization kinetics, thermal behavior, and GFA of (Cu50Zr43Al7)98Y2 BMG, emphasizing its potential in materials science applications.

A modified maxwell-pulse thermoplastic constitutive model of in-situ Ta-particle reinforced Zr-based bulk metallic glass composites

The impact of different Ta contents on the mechanical properties and thermoplastic forming ability of in-situ Ta-particle reinforced Zr–Cu–Al–Ni bulk metallic glass composites was studied. The composition (Zr55Cu30Al10Ni5)94Ta6 with the best comprehensive performance was chose for a systematic investigation into its thermoplastic behavior in the supercooled liquid region (SLR), with quantitative analysis conducted by the strain rate sensitivity index and activation volume. The steady-state flow stress and the stress overshoot intensity were augmented with deformation temperature decreasing, strain rate increasing, and the addition of the secondary phase, leading to a transition from Newtonian to non-Newtonian flow regime. The addition of the secondary phase deteriorated the rheological properties of the material. To solve the problem that the Maxwell-Pulse constitutive model showed an inability to accurately describe the steady-state flow process. A modified constitutive relationship, introducing the effect of the volume fraction of Ta particles on viscosity and elastic modulus in the steady-state flow process which was ignored in Maxwell-pulse model, was established. The fitting results of the true stress-strain curves of the modified Maxwell-pulse constitutive model were in better agreement with the experimental date than those of the Maxwell-pulse constitutive model, with higher prediction accuracy. The modified constitutive model well predicted the thermoplastic deformation behavior of (Zr55Cu30Al10Ni5)94Ta6. The influence mechanism of Ta particles on the flow behavior was explained that Ta particles increased the viscosity of amorphous matrix, thereby hindering its flow and ultimately leading to an increase in flow stress.

Composition design and crystallization behavior of Zr–Cu–Ni–Al bulk metallic glasses

The Zr–Cu–Ni–Al system was explored in this study, and seven new compositions of Zr-based bulk metallic glasses (BMGs) were designed by combining different proportions of binary eutectic phases Zr38Cu62, Zr76Ni24 and Zr51Al49, and rod-like shape samples were prepared with different diameters using the copper mold casting method. Modifying the proportion coefficient of these eutectic units, the width of the supercooled liquid region was increased from 79 to 95 K, and the thermal stability of the prepared metallic glass was improved. Differential scanning calorimetry was used to investigate the non-isothermal and isothermal crystallization behavior of the prepared samples. Noticeably, there was a small low-temperature exothermic peak before the glass transition temperature Tg in the non-isothermal crystallization process, which was related to the structural relaxation. The crystallization transition activation energy fitted by the Kissinger equation had the same variation trend as that obtained by the Arrhenius equation. Among the four metallic glasses studied, the glassy phase of Zr55·5Cu23·25Ni9Al12.25 was more stable, showing higher glass transition activation energy and longer incubation time. In addition, the isothermal crystallization processes of four metallic glasses were studied according to the Johnson-Mehl-Avrami (JMA) model. The calculated average Avrami exponents were >2.5, indicating that the nucleation rate increased during the isothermal crystallization process.

Evolution of short-range order and dynamics of medium-range order influence on the glass-forming ability of CuZrAg alloys

The glass-forming ability (GFA) of metallic glasses (MGs) is influenced by both short-range order (SRO) and medium-range order (MRO). However, experimentally examining the dynamic evolution of these microstructures across various time scales remains challenging. Therefore, this study employs molecular dynamics (MD) simulations to investigate the evolution of SRO and relaxation dynamics of MRO impacting on the GFA of Cu60Zr40-xAgx (x = 5, 10, 15, 20, 25) ternary alloys during their rapid solidification process. The GFA is characterized by the width of the supercooled liquid region, with Cu60Zr35Ag5 exhibiting the most prominent GFA among the five alloys. The reverse tracking method was utilized to analyze the inheritance and transformation of defective icosahedral clusters within the SRO. The defective icosahedral heritability and transformation rate are indicative of a more ordered and stable structure, significantly influencing the GFA. Furthermore, the decrease of Ag content leads to the increase of the average size of MRO clusters. The systems with larger MRO nanoclusters exhibit pronounced dynamic heterogeneity and a robust “cage effect”, thus hindering crystallization and promoting GFA. This study approaches GFA analysis from a microstructural evolution and dynamics perspective, aiming to provide theoretical backing for the discovery of alloys with superior GFA.

Plastic quasicrystal-containing alloys prepared by annealing pseudo-high entropy Zr70–75(Al, Ni, Cu, Ag)25–30 glassy alloys

A glassy (G) phase was formed for Zr-rich Zr70–75(Al, Ni, Cu, Ag)25–30 (atomic percent, at.%) melt-spun alloy ribbons. These glassy alloys exhibit the glass transition, followed by a supercooled liquid region and then three-stage crystallization. The glass transition temperature and the onset temperature for the first-stage crystallization (Tx1) decrease from 630 to 668 K, respectively for the 70Zr alloy to 619 and 652 K, respectively for the 75Zr alloy. The first-stage exothermic peak is due to the precipitation of an icosahedral quasicrystal (IQ) phase. The IQ particle size decreases from 10 nm to 6 nm with increasing Zr content from 70at.% to 74at.%. The [G + IQ] phases change to Zr2Ni + Zr2(Cu, Ag) phases after the second exothermic peak and then Zr2Ni + Zr2(Cu, Ag) + Zr5Al3 phases after the third stage. It is noticed that the as-spun glassy alloy ribbons as well as the annealed [G + IQ] phase ribbons exhibit good bending plasticity. Furthermore, the 70Zr thicker ribbons also exhibit high tensile fracture strength of 1090–1187 MPa and plastic elongation of 0.17 %–0.42 %. The fracture mode is similar to that of ordinary bulk metallic glasses. The Vickers hardness (Hv) is 480 for 70Zr alloy and decreases to 436 for 75Zr alloy. The precipitation of IQ phase causes a significant increase in Hv to about 554. The formations of glassy alloys with high Zr contents of 70at.%–75at.% by melt spinning as well as the [G + IQ] phase alloys with good bending plasticity by annealing hold promise for the creation of a new type of engineering material, transcending mere academic novelty.

Evolution of the supercooled liquid region and STZ in laser assisted scratching Cu50Zr50 amorphous alloy

Evolution of the supercooled liquid region and STZ in laser assisted scratching Cu50Zr50 amorphous alloy

Structure and Properties of Na2S-SiS2-P2S5-NaPO3 Glassy Solid Electrolytes.

In the development of sodium all-solid-state batteries (ASSBs), research efforts have focused on synthesizing highly conducting and electrochemically stable solid-state electrolytes. Glassy solid electrolytes (GSEs) have been considered very promising due to their tunable chemistry and resistance to dendrite growth. For these reasons, we focus here on the atomic-level structures and properties of GSEs in the compositional series (0.6-0.08y)Na2S + (0.4 + 0.08y)[(1 - y)[(1 - x)SiS2 + xPS5/2] + yNaPO3] (NaPSiSO). The mechanical moduli, glass transition temperatures, and temperature-dependent conductivity were determined and related to their short-range order structures that were determined using Raman, Fourier transform infrared, and 31P and 29Si magic angle spinning nuclear magnetic resonance spectroscopies. In addition, the conductivity activation energies were modeled using the Christensen-Martin-Anderson-Stuart model. These GSEs appear to be highly crystallization-resistant in the supercooled liquid region where no measurable crystallization below 450 °C could be observed in differential scanning calorimetry studies. Additionally, these GSEs were found to be highly conducting, with conductivities on the order of 10-5 (Ω cm)-1 at room temperature, and processable in the supercooled state without crystallization. For all these reasons, these NaPSiSO GSEs are considered to be highly competitive and easily processable candidate GSEs for enabling sodium ASSBs.

Soft magnetism enhancement and eddy current suppression in bioinspired Iron‐based nanocrystalline soft magnetic composites with nacre‐like structure

Bioinspired nacre-like structured high-density soft magnetic composites (SMCs) have been successfully constructed using flaky-Fe73.8Si13.5B8.7Cu1Nb3 powders in the supercooled liquid region (SCLR). These densely arranged particles with a consistent planar orientation significantly enhance the soft magnetic properties of SMCs, including high permeability and low magnetic losses. The internal structures of the composites and microstructure evolution of the flaky nanocrystalline particles during the hot-pressing process have been thoroughly studied. Moreover, systematic investigations into the effects of coatings and particle sizes on the maximum permeability and magnetic losses of the composites are conducted. The SMC prepared using the coated particles with a size of 0–100 µm exhibits a high maximum permeability of 2170 (at 1000 Hz) and low magnetic loss of 41.61 W kg–1 (at 1000 Hz and 1.0 T). The losses and permeability analysis reveal that the superior performance of these soft magnetic materials is attributed to their laminated structure, insulation coating, and the reduced planar demagnetizing factor. Compared to the traditional silicon steel, this novel SMCs exhibits high magnetic permeability and reduced magnetic losses at frequencies above 1000 Hz, which possess immense application potential within high-frequency electric machines.

Effect of Chemical Composition on the Thermoplastic Formability and Nanoindentation of Ti-Based Bulk Metallic Glasses.

A series of Ti41Zr25Be34-xNix (x = 4, 6, 8, 10 at.%) and Ti41Zr25Be34-xCux (x = 4, 6, 8 at.%) bulk metallic glasses were investigated to examine the influence of Ni and Cu content on the viscosity, thermoplastic formability, and nanoindentation of Ti-based bulk metallic glasses. The results demonstrate that Ti41Zr25Be30Ni4 and Ti41Zr25Be26Cu8 amorphous alloys have superior thermoplastic formability among the Ti41Zr25Be34-xNix and Ti41Zr25Be34-xCux amorphous alloys due to their low viscosity in the supercooled liquid region and wider supercooled liquid region. The hardness and modulus exhibit obvious variations with increasing Ni and Cu content in Ti-based bulk metallic glasses, which can be attributed to alterations in atomic density. Optimal amounts of Ni and Cu in Ti-based bulk metallic glasses enhance thermoplastic formability and mechanical properties. The influence of Ni and Cu content on the hardness of Ti-based bulk metallic glasses is discussed from the perspective of the mean atomic distance.

The rheological behavior and constitutive model of Zr35Ti30Be27·5Cu7.5 metallic glass under high strain rate tensile conditions within the supercooled liquid region

Tensile rheological behavior of the Zr35Ti30Be27·5Cu7.5 metallic glass under conditions of high strain rates (strain rates ranging from 0.05 s−1 to 0.5 s−1) within the supercooled liquid region was studied. The stress-strain curve reveals that this metallic glass demonstrates non-Newtonian flow characteristics under these circumstances. The peak stress associated with stress overshoot increases as temperature decreases and strain rate increases. However, the steady-state flow stress displays an anomalous decrease due to rapid necking at high strain rates. Subsequently, the thermal processing map of the Zr35Ti30Be27·5Cu7.5 metallic glass was established and analyzed. It reveals that the alloy has relatively excellent thermoplastic forming ability at temperature between 630 K and 655 K and strain rates between 0.05 s−1-0.2 s−1. We found that under strain rates ε˙≥10−2s−1, the strain rate is the primary factor influencing normalized viscosity. Therefore, we developed a simplified Maxwell-Pulse constitutive model applicable to metallic glass in the supercooled liquid region under high strain rate conditions, by simplifying the constitutive equation for steady-state flow stress using a simplified formula for normalized viscosity calculation. The predictions of this simplified modified model align well with experimental values. By comparing the simplified and unsimplified Maxwell-Pulse constitutive models, the overall fitting accuracy of the simplified model was improved by 3–5%, with the highest improvement of 67% in the steady-state flow stress stage. These results indicate that the modified model accurately reflects the stress-strain relationship for the Zr35Ti30Be27·5Cu7.5 metallic glass under high temperature and high strain rate tensile conditions.

Influence of gadolinium content on magnetic property and oxidation mechanism of Fe-B-Nb-Gd metallic glass

In this work, we use the rapid solidification technique to prepare five kinds of metallic glasses with different Gd content, and investigate in depth the influences of Gd content on the amorphous formation capability, thermal stability, and magnetic properties of (Fe<sub>73</sub>B<sub>22</sub>Nb<sub>5</sub>)<sub>100–<i>x</i></sub>Gd<sub><i>x</i></sub> (<i>x</i> = 0, 0.5, 1.0, 1.5, 2.0) alloys. By comparing the microstructural morphology and solute distribution of oxidation products before adding Gd and those after adding Gd, the amorphous oxidation mechanism is analyzed systematically. With the addition of Gd, the atomic size difference of the alloys exceeds 13%, and the configuration entropy increases from 7.27 kJ/(mol·K) to 9.44 kJ/(mol·K). The glass-forming ability of the alloy is significantly improved. The increase of Gd content can increase the glass transition temperature of the alloy to 864 K, and the undercooled liquid region can reach 73 K, significantly enhancing the thermal stability of the metallic glasses. The Gd limits the local anisotropy of the alloy and reduces the density of quasi-dislocation dipole defects. This can effectively reduce the pinning sites that hinder the rotation of magnetic domain walls, thereby improving the soft magnetic property. By comparing with the metallic glasses without Gd, only 2% (atomic percentage) Gd can reduce the coercivity by 8%. Moreover, the Gd makes the metallic glasses more sensitive to temperature variation in the oxidation process, and the temperature of the maximum oxidation rate is reduced by 15 K. However, their antioxidant performance does not deteriorate. The Gd atoms are influenced by binding energy and migrate to the surface, forming Gd-rich oxides. They fill surface defects and occupy a large part of the top space, leading to the structure becoming more compact near the surface. This structure reduces the channels for oxygen atoms to diffuse through the microstructure interface, which helps to improve antioxidant capability. This work provides a new approach for designing high performance Fe-based metallic glasses.

Superplastic Forming of Zr-Based Bulk Metallic Glasses

In this paper, the partially crystallized Zr70Cu13.5Ni8.5Al8 bulk metallic glasses (BMGs) were prepared, and their superplastic deformation ability in the supercooled liquid region was studied via compression over a wide range of strain rates from 5 × 10−4 s−1 to 1 × 10−2 s−1. It has been found that the superplastic deformation behavior of the BMGs is strongly dependent on the strain rate and temperature. The flow behavior of the BMGs transformed from Newtonian fluid to non-Newtonian fluid with the increase in the strain rate and the decrease in temperature. Based on the high-temperature compression results, a thermalplastic forming map was constructed, and the optimal superplastic forming parameters were obtained. Then, gears were successfully extruded using part of the optimal thermal processing parameters. Further studies showed that high-temperature extrusion induced the crystallization of the BMGs, which increased the microhardness of the gears.

Effect of overheating-induced minor addition on Zr-based metallic glasses

Melt treatment is well known to have an important influence on the properties of metallic glasses (MGs). However, for the MGs quenched from different melt temperatures with a quartz tube, the underlying physical origin responsible for the variation of properties remains poorly understood. In the present work, we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins. Specifically, we quenched the melt at different temperatures ranging from 1.1T l to 1.5T l (T l is the liquidus temperature) to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating. We found that glass transition temperature, T g, increases by as much as 36 K, and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5T l. The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys. The incorporated oxygen and silicon can both enhance the interactions between atoms, which renders the cooperative rearrangements of atoms difficult, and thus enhances the kinetic stability of the MGs.

Effects of rare-earth element Y content on the microstructure and properties of quinary Al–Ni–Zr–Co–Y high entropy metallic glasses

A series of quinary (Al1/4Ni1/4Zr1/4Co1/4)100-xYx (x = 16–28 at.%) high entropy metallic glass ribbons were successfully fabricated through the high-speed single roller melt-spinning method. The effects of rare-earth element yttrium content on the microstructure and performances of alloy ribbons were systematically investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), heat treatment, transmission electronic microscopy (TEM), atomic force microscopy (AFM) and electrochemical experiments. The microhardness of metallic ribbons was measured by Vickers hardness tester. Results show that the microstructure of the as-quenched alloy ribbons maintain the glassy state and the average microhardness value of each specimen can reach 488 HV0.1 or above. The surface morphologies of the as-spun ribbon samples exhibit the smooth surface with small roughness value of Ra = 0.115–0.150 nm. In the meantime, with the increase of Y content, the glass transition temperature can be detected in the DSC traces when Y content is over 22 at.%, and the crystallization onset temperature shifts to the lower temperature region, suggesting that the thermal stability of amorphous state in Al–Ni–Zr–Co–Y alloy ribbons has been weakened. The (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons own the highest crystallization onset temperature (∼742 K). Adding appropriate yttrium element can enlarge the super-cooled liquid region and improve the glass-forming ability. In 3.5 wt% NaCl solution, the prepared alloy ribbons can maintain smaller corrosion current densities (∼10−8 A cm−2) than traditional Al-based amorphous alloys, 6061 Al alloy and other common structural steels. The X-ray photoelectron spectrometer results indicate that the passive film of equiatomic alloy ribbons is rich in oxides of Al, Zr, Co, and Y elements, which has excellent resistance to chloride ion attack. On the basis of all experimental results, (Al1/4Ni1/4Zr1/4Co1/4)84Y16 alloy ribbons can optimally combine outstanding corrosion resistance, superior thermal stability, and acceptable microhardness. The above research results lay a solid foundation for the composition development of high-performance high entropy metallic glasses.

Crystallization kinetics and nanoindentation studies of Cu46Zr40Ti8.5Al5.5 glassy alloy

Crystallization kinetics of Cu46Zr40Ti8.5Al5.5 metallic glass is investigated in non-isothermal and isothermal conditions. In non-isothermal condition, the crystallization activation energy is determined using Kissinger's method. Further, activation energy of reported Cu-Zr-Al metallic glasses are compared with Cu46Zr40Ti8.5Al5.5 alloy to understand the effect of Ti addition on crystallization kinetics. Detailed investigation on activation energy through the crystallization process is studied. To understand the influence of nucleation and growth mechanism during the crystallization steps, samples are heated in isothermal conditions at various annealing temperatures in supercooled liquid region to determine the local Avrami's exponent using Johnson-Mehl-Avrami equation. Additionally, small scale mechanical response is noted on metallic glass sample to determine the influence of structure on hardness and elastic modulus. Nanoindentation results showed hardness value of 5.39 ± 0.09 GPa and Young's modulus of 92.81± 0.52 GPa.