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Bulk metallic glasses synthesized at specialized facilities at Yale using magnetron cosputtering are sent to Southern Connecticut State University for elemental characterization. Characterization is done using a Zeiss Sigma VP SEM coupled with an Oxford EDS. Characterization is automated using control software provided by Oxford. Collected data is processed and visualized using computational methods developed internally. Processed data is then organized into a database suitable for web retrieval. This technique allows for the rapid characterization of a combinatorial wafer to be carried out in ~11 hours for a single wafer containing ~600 unique compounds.

Crystallization and melting behaviors of the Nd₆₀Al₁₀Fe₂₀Co₁₀ bulk metallic glass (BMG) have been studied by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). It is found that the BMG exhibits a melting process before the crystallization when the heating rate is larger than 20 K/min and the anomalous melting and crystallization behaviors are attributed to the partially melted phase due to primary crystallization. The kinetics of the main crystallization exclusive of the effect of melting process is studied by subtracting the heating behaviors from the DSC traces of the as-cast rod.

Fe-based bulk amorphous rods of 3 mm in diameter and a composition of Fe₄₁Cr₁₅Mo₁₄C₁₅B₆Y₂Co₇ were produced by copper mold casting. The as-cast amorphous rods contain a small (2%) fraction of pores. To close the pores, samples cut from the amorphous rods were hot isostatically pressed (hipped) at 863 K, which is in the supercooled liquid temperature range between the glass transition temperature and the crystallization temperature of the amorphous phase, and under a pressure of 200 Mpa. Microstructure examination of the hipped samples shows that hipping results in an increase of the density of the samples from 7.9 g/cm³ to 8.0 g/cm³, and a decrease of the porosity level from 2% to 1%, and that a very small fraction of unknown crystalline phase form. As a result of these microstructure change caused by hipping, the average room temperature compressive fracture strength of the bulk metallic glass (BMG) decrease from 3500 Mpa to 3000 MPa, while the strain to fracture changes little from 1.5% to 1.4%. The mechanisms of the effect of hipping on microstructure and mechanical properties of the Fe-based BMG are discussed.

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications under impact loading. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation to a Zr-based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact or shock loading conditions. Results were compared with those of spherical indentation under quasi-static and impact loading and were discussed. The interface bonded specimen method was adopted in order to observe the subsurface damage, especially the formation of shear bands induced during indentation under different loading conditions.

Shear banding characterization of Zr_64.13Cu_15.75Ni_10.12Al₁₀ and Zr₆₅Cu₁₅Ni₁₀Al₁₀ bulk metallic glasses (BMGs) with significant difference in inherent plasticity and quite similar chemical composition was studied by depth sensitive macroindentaion tests with conical indenter. Well-developed shear band pattern can be found for both BMGs after indentation. Distinct difference in the shear band spacing, scale of plastic deformation region and the shear band branching in the two BMGs account for the different plasticity.

TEM investigations on crystallization behavior of a Fe₆₈C_10.5Si_4.4B_6.5P_8.6Al₂ bulk metallic glass reveals that the nano-scale fcc Fe phase formed by primary crystallization is homogeneously embedded in the amorphous matrix after heat treatment at 783 K for 30 min. With increasing heat treatment time (783 K for 45 min), a tetragonal Fe₃(C,B,P) phase encapsulates the primary fcc Fe phase suppressing the growth of the fcc Fe phase. The Fe₃(C,B,P) phase decomposes into a mixture of orthorhombic Fe₃(C,P) and tetragonal Fe₃(B,P) upon further annealing treatment at 783K.

Bulk metallic glasses (BMGs) in pseudo-ternary (La-Ce)-Al-Cu system with high glass-forming ability (GFA) were synthesized based on the beneficial effect of the coexistence of similar elements La and Ce with similar atomic size and various valence electronic structures on GFA. With the coexistence of La and Ce in (La_xCe_1-x)₆₅Al₁₀Cu₂₅ system, bulk metallic glasses with diameters up to 12 mm can be produced by copper mold casting. Besides the high GFA, the (La_xCe_1-x)₆₅Al₁₀Cu₂₅ BMGs with x = 0.6 and 0.7 exhibit low glass transition temperature T_g around 362 K and wide supercooled liquid regions ΔT_x (ΔT_x = T_x - T_g, where T_x is the onset temperature of crystallization) of about 80 K. Compared with ternary La-Al-Cu and Ce-Al-Cu systems, significant improvement of GFA for the (La-Ce)-Al-Cu system is caused by the coexistence of similar elements La and Ce, and the mechanism is discussed from a thermodynamic viewpoint.

In this study, the cracking behavior in the bulk and the stress-strain responses of partially crystallized Zr-Ti-Cu-Ni-Be bulk metallic glass after surface modification were investigated. The compressive plasticity was found to be dependent on the surface conditions. The plasticity was enhanced significantly by a complete removal of visible surface flaws. The electro-plating of copper on the rough surface also increased the plasticity of Zr base BMG of the present study. The beneficial effect of the electro-plating can be attributed to filling and smoothening effect due to plating and/or the ductilization of the surface, both of which does not favor crack nucleation. We also found the cracking behavior in the bulk different from the surface region. The cracks in the center of the sample were not straight, but wavy, suggesting the cracks were deflected by or attracted to crystalline particles. A high magnification view of a crack revealed small triangular shaped crystals along the crack path.

In order to define the relation between yield behavior and yield criterion of bulk metallic glass (BMG), analysis and investigations have been carried out for interrelations between yield strengths and the angle which fracture plane deviates from the 45° plane of the maximum shear stress in tensile and compressive test of BMG. Tensile fracture angle is consistent with the result calculated by theory of disconnected slip line field and Mises yield condition. Compressive fracture angle is consistent with the result calculated by Coulomb yield condition. Conclusion: BMG obeys different yield criterions in different stress states. For tensile, it follows Mises criterion, and for compression, it follows Coulomb criterion.

The effect of alloy composition on improving glass-forming ability of La-based alloys is investigated in this work. Previous composition criteria demonstrated that the alloys with high glass-forming ability should have negative heats of mixing among the main constituent elements. In this study, the addition of Fe to a La-based La-Al-Ni-Cu alloy significantly improved the glass-forming ability, although the heat of mixing between Fe and the main element La is positive. La-Al-Ni-Cu-Fe bulk metallic glasses with diameters up to 15 mm were prepared by the method of pouring the molten alloys into a copper mold. These La-Al-Ni-Cu-Fe bulk metallic glasses exhibit relatively wide supercooled liquid region of about 50 k, and high T_rg(T_g/T_l) and γ(T_x/(T_g+T_l)) values. It is found that the addition of Fe to the La-Al-Ni-Cu alloy lowers the Gibbs free energy difference between the liquid and crystalline phases in the supercooled liquid region and enhances the glass-forming ability of the alloy.

Structural relaxation by isothermal annealing below the glass transition temperature is conducted on a Zr_64.13Cu_15.75Ni_10.12Al₁₀ bulk metallic glass. The effect of structural relaxation on thermal and mechanical properties was investigated by differential scanning calorimetry and instrumented nanoindentation. The recovery of the enthalpy in the DSC curves indicates that thermally unstable defects were annihilated through structural relaxation. During nanoindentation, the structural relaxation did not have a significant influence on the serrated plastic flow behavior. However, Structural relaxation shows an obvious effect in increasing both the hardness and elastic modulus, which is attributed to the annihilation of thermally unstable defects that resulted from the relaxation.

Till now, the developed centimeter-sized Ti-based bulk metallic glasses (BMGs) always consist of at least five elements. We report that Ti₄₁Zr₂₅Be₂₈Fe₆ quaternary glassy alloy can be made up to 10 mm in diameter by water quenching, while only ϕ 8 mm fully glassy rod can be obtained by copper mould suction casting. This alloy possesses fewer constituent elements, wider supercooled liquid region and higher specific strength than other developed centimeter-sized Ti-based BMGs and has wide prospect for practical application. Our results also indicate that for Ti₄₁Zr₂₅Be₂₈Fe₆ alloy which possesses relatively strong glass-forming ability, reducing the heterogeneous impurities in the melt is more effective to obtain fully glassy samples than increasing the cooling rate merely.

In this work, we studied the effect of micro-alloying on the glass-forming ability (GFA) and magnetic properties of ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{25}$ bulk metallic glass (BMG). By minor Fe substitution for Ni, we obtained ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG with enhanced magneto-caloric effect (MCE) and GFA similar to ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{25}$ BMG. The maximum magnetic entropy change $(-\mathrm{\Delta }{S}_m^{\mathrm{\text{peak}}})$ and the magnetic refrigerant capacity ($R_c)$ of ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG within the field range of 5 T are about 9.05 J kg${}^{-1}$ K${}^{-1}$ and $850\mathrm{\text{J}}\cdot {\mathrm{\text{kg}}}^{-1}$, respectively, both of which are larger than the values of ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Ni}}}_{25}{\mathrm{\text{Al}}}_{20}$ BMG. The mechanism for the improved MCE of the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG was investigated and the magneto-caloric behaviors were studied by constructing the field dependence of $-\mathrm{\Delta }{S}_m^{\mathrm{\text{peak}}}$ of ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Ni}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG.

A Ni–Fe–B–Si–Nb amorphous alloy was deposited on a steel substrate surface via a laser cladding process, and a laser cladding plus laser remelting process. The wear behavior of the laser processed samples and the bulk metallic glass (BMG) sample with the same nominal composition were tested using a pin-on-disc type testing machine. The nano-mechanical properties of the samples were measured with a nano-characterization system. The friction wear tests showed that deep grooves and wear debris were formed on the worn surface of the laser cladded coating, while only shallow grooves for the laser remelted coatings. The friction coefficients of laser remelted coatings and BMG were lower than the laser cladded coating. The wear mass losses of the laser remelted coating were less than the BMG when the laser remelting scanning speed was higher than 6 mm/min. The nano-hardness and elastic modulus of the remelted coating is higher than that of the laser cladded coating. Also, they increase with the increasing laser scanning speed with 1227.9 HV and 277.4 GPa when the remelting scanning speed is 8 m/min. Based on the nano-indentation and friction wear tests results, it was found that the friction wear properties of the laser cladded coating, laser remelted coatings and BMG related well to the ratio of H³/E². A higher value of H³/E² can lead to a better wear resistance property.

The mechanical-annealing referred in this work is also named pre-strain, which is widely investigated in TRIP steel, stainless steel, magnesium alloy and aluminum alloy. In this case, we used preloading to input energy into a bulk metallic glass (BMG) to observe the changes in the structure and mechanical properties. We selected Zr${}_{56}$Co${}_{26}$Al${}_{18}$ BMG as a model material owning to its outstanding glass forming ability and excellent mechanical properties. The samples were kept at a constant pressure of 1900, 1700 and 1500 MPa (below the yield strength) for 40, 55 and 70 h. The study found out that the density of those samples increased after being pre-loaded. Then, the samples underwent aging treatment at room-temperature for more than 30 days after unloading. After re-compressing the samples, the results show that the yield strength and fracture strength of the samples decreased, and the amplitude of the serrated plastic flow increased during the plastic stage. Our finding might have some implications for understanding the plastic deformation of BMGs.

Bulk metallic glasses are often used well below their glass transition temperatures, T_g, because of their change in the physical properties of the material through its glass transition, which is not considered a phase transition; rather it is a phenomenon extending over a range of temperature and is defined by a viscosity threshold of 10¹² Pa ⋅ s. In this work, a Zr-based metallic glass upon annealing below glass transition temperature (T_g–30 K) was quasi-in-situ investigated. The structural and elastic properties were observed carefully by utilizing an in-house designed density testing device and an ultrasonic testing device. We found out that the density, the shear velocity, the longitudinal wave velocity, and the elastic modulus increased through annealing at 719 K for 300, 900 and 1500 s. A possible explanation was presented based on the free volume theory and it was found that the relaxation kinetics in this study obeyed the Kohlraush–Williams–Watts (KWW) relaxation function with $\beta$ = 0.420 $<$ 1 implying that the relaxation mechanisms were multiple ones.

Paramagnetic Nd₆₀Co_40-xAl_x(x=5, 10, 15) bulk metallic glasses (BMGs) were prepared in the shape of rods 2 mm in diameter by suction casting. The ternary alloys have shown distinct glass transitions in Differential Scanning Calorimetry (DSC) measurements and excellent glass-forming ability. The glass transition and crystallization behaviors as well as their kinetics have been studied. The reduced glass transition temperature and the supercooled liquid region of the alloys were found to increase with the increasing content of Al. The role of Al was discussed. The parameter γ defined by Liu et al. was employed to discuss the glass-forming ability of the alloys and the critical cooling rates as well as the critical section thickness of the alloys were predicted accordingly.

In this work, we studied the thermal stability and kinetics of Nd₅₅Al₂₀Fe₂₅ bulk metallic glass (BMG) with distinct glass transition and multistage crystallizations. The kinetics of glass transition and crystallizations were investigated using the Kissinger method and the ideal glass transition temperature of the alloy was obtained via Lasoka's equation. The thermal stability of the BMG was investigated by means of continuous transformation diagrams obtained from the extension of Kissinger analysis. It is suggested that the stability limit of the supercooled liquid, i.e. Kauzmann temperature, could also be regarded as the long-term stability criteria of the BMG.

By adding 2 at.% Al element in Zr₅₀Cu₅₀ binary glass-forming alloy, we obtained Zr₅₀Cu₄₈Al₂ glassy rods with diameter larger than 3 mm. The reduced glass transition temperature, parameter γ and the critical section thickness obtained from the differential scanning calorimetry (DSC) traces indicate the better glass-forming ability (GFA) of Zr₅₀Cu₄₈Al₂ bulk metallic glass (BMG). The super-cooled liquid region and the continuous heating transformation diagram constructed from Vogel–Fulcher–Tammann fitting of crystallization temperature illustrate the enhanced thermal stability of the Zr₅₀Cu₄₈Al₂ BMG. The mechanism of effect of minor Al addition on GFA was investigated in more detail from Angell's fragility concept and from the thermodynamic point of view respectively.

${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ bulk metallic glass (BMG) exhibits good glass forming ability (GFA) and excellent magneto-caloric effect (MCE). In order to further improve the GFA and MCE of the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ BMG, we attempted to add small amount of Fe as a replacement of Co in the BMG and obtained ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ glassy rod using a traditional suction casting method. The ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG shows a better GFA and MCE than the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ BMG. The magneto-caloric behavior of the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG was investigated by studying the field dependence of the magnetic entropy change peak and the refrigeration capacity.