Enthalpy Relaxation Kinetics of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 Supercooled Liquid Close to the Glass Transition

2003 ◽  
Vol 806 ◽  
Author(s):  
Minalben B. Shah ◽  
Ralf Busch
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Enthalpy Relaxation ◽  
Medium Size ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Relaxation Kinetics ◽  
State Diffusion

ABSTRACTIsothermal relaxation studies of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass forming alloy were performed using Differential Scanning Calorimetry in the glass transition and the supercooled liquid region. A new experimental method was developed to study the isothermal enthalpy relaxation kinetics. The results reveal that the enthalpy relaxes in an Arrhenius fashion. The activation energy obtained from the Arrhenius fit is comparable to the activation energy required for the diffusion of the medium size atoms. This suggests that the solid-state diffusion governs the enthalpy relaxation process. The stretching exponents for the relaxation are close to unity, which indicates that the alloy is a rather strong glass former.

GLASS FORMING ABILITY AND KINETIC CHARACTERS OF PARAMAGNETIC Nd60Co40-xAlx(x=5, 10, 15) BULK METALLIC GLASSES

2004 ◽  
Vol 18 (14) ◽  
pp. 679-685 ◽  
Author(s):  
L. XIA ◽  
Y. D. DONG
Keyword(s):  
Glass Transition ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Glass Forming Ability ◽  
Ternary Alloys ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Glass Forming

Paramagnetic Nd 60 Co 40-x Al 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.

Microstructure and Microhardness in Current Annealed Fe65.5Cr4Mo4Ga4P12C5B5.5 Bulk Metallic Glass

2007 ◽  
Vol 555 ◽  
pp. 521-526 ◽  
Author(s):  
N. Mitrović ◽  
B. Čukić ◽  
Branka Jordović ◽  
Stefan Roth ◽  
M. Stoica
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous State ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Nominal Composition ◽  
Liquid Region ◽  
Scanning Calorimetry

The rods of Fe-based bulk metallic glasses with the nominal composition Fe65.5Cr4Mo4Ga4P12C5B5.5 were cast by melt injection into 1.5 and 1.8 mm diameter copper molds. The thermal stability, microstructure and crystallization behavior were investigated by differential scanning calorimetry, optical micrography and X-ray diffraction, respectively. The wide supercooled liquid region between crystallization temperature (Tx) and glass transition temperature (Tg) in the as-cast state Tx=Tx-Tg=60 K, as well as the high value of reduced glass transition temperature Trg=Tg/Tl=0.567 (Tl is liquidus temperature) approves enhanced thermal stability of the alloy against crystallization. In the as-cast “XRD-amorphous” state, microhardness HV1=742 was observed. Multistep current annealing thermal treatments were performed for structural relaxation. After applying high enough heating power per square area (PS ≥ 6 W/cm2), intensive crystallization of the samples characterized by appearance of several iron-metalloid compounds (Fe5C2, Fe3Ga4, Fe63Mo37 and Mo12Fe22C10) was observed. The microstructure changes after crystallization bring about differences in the microhardness values. The areas of still present amorphous matrix are with increased value HV1=876, but a remarkable decrease to HV1=323 was observed in precipitated crystallized zone that propagate along inner part of cylinders.

Amorphization and thermal stability of mechanically alloyed Zr54Cu19Ni8Al8Si5Ti5O1

2005 ◽  
Vol 903 ◽  
Author(s):  
Vassilios Kapaklis ◽  
Athanasios Georgiopoulos ◽  
Peter Schweiss ◽  
Constantin Politis
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Supercooled Liquid ◽  
High Energy ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Arc Melting ◽  
Thermal Stability Of

AbstractIn the present work we have intentionally introduced significant amount of oxygen to Zr- based alloys. Samples were prepared either by high energy ball milling of the elemental powders and single phase α-ZrO0.43 at the appropriate stoichiometry, or by melting in an Zr-gettered arc melting facility, in both cases under purified argon atmosphere. The effect of small amounts of oxygen (∼1 at. %) on the amorphization process and the thermal stability of mechanically alloyed Zr54Cu19Ni8Al8Si5Ti5O1 powders and arc melted bulk samples was studied by X-ray diffraction and differential scanning calorimetry. It was found that the introduction of oxygen to the alloy composition does not inhibit the amorphization but enhances greatly the thermal stability of the mechanically alloyed amorphous powders. Compared to samples without oxygen prepared either by arc melting or mechanical alloying, samples with oxygen show an increase of the supercooled liquid region from ΔTx−g=Tx−Tg=117 °C to 141 °C where Tx is the crystallization and Tg the glass transition temperature. The glass transition for the mechanically alloyed samples (Tgma) remains unaffected at 336 °C.

The Effect of Iron and Oxygen Additions on the Properties of Zr-Al-Cu-Ni Bulk Metallic Glass Forming Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
J. Eckert ◽  
N. Mattern ◽  
M. Seidel ◽  
L. Schultz
Keyword(s):  
Glass Transition ◽  
Oxygen Content ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Coarse Grained ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Fe Content

ABSTRACTThe effect of iron and oxygen additions on the thermal stability of rapidly quenched amorphous Zr65Al7.5Cu17.5Ni10) was studied by x-ray diffraction and differential scanning calorimetry. With increasing Fe content the glass transition temperature Tg and the crystallization temperature Tx shift to higher temperatures. The increase is more significant for Tg than for Tx, resulting in a decrease of the supercooled liquid region with increasing Fe content. For oxygen additions Tx decreases with increasing oxygen content whereas Tg increases slightly, causing a decrease of the supercooled liquid region with increasing oxygen content. The results reveal that even minor iron or oxygen contaminations lead to drastic changes in the glass transition behavior and the crystallization mode. Large iron or oxygen contents lead to the formation of nanocrystalline microstructures instead of coarse-grained material.

Thermal Stability and Crystallization Kinetics of Ti40Zr10Cu34Pd14Sn2 Bulk Metallic Glass

2012 ◽  
Vol 188 ◽  
pp. 3-10 ◽  
Author(s):  
Mariana Calin ◽  
Mihai Stoica ◽  
Na Zheng ◽  
Xiao Rui Wang ◽  
Sergio Scudino ◽  
...  
Keyword(s):  
Activation Energy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Crystallization Process ◽  
Primary Crystallization ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Diffusion Controlled

In this work, the isochronal and isothermal activation energies for the primary crystallization process of Ti40Zr10Cu34Pd14Sn2bulk metallic glass have been studied by differential scanning calorimetry and determined using the Kissinger approach and the Johnson-Mehl-Avrami analysis, respectively. The activation energy for crystallization evaluated by the Kissinger method is 253 kJ/mol. Similar activation energy for crystallization was obtained from the viscosity measurements. The values of the differential Avrami exponent are also determined from the isothermal data. Assuming diffusion-controlled growth, it is shown that thermal treatment of the samples in the supercooled liquid region considerably influences the behavior of the nucleation rate during the crystallization process.

Synthesis, Crystallization Behavior and Surface Modification of Ni-Cr-Si-Fe Amorphous Alloy

2012 ◽  
Vol 510-511 ◽  
pp. 137-142 ◽  
Author(s):  
Muhammad Iqbal ◽  
J.I. Akhter ◽  
M.U. Rajput ◽  
K. Mahmood ◽  
Z. Hussain ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Surface Modification ◽  
Glass Transition ◽  
Transition Temperature ◽  
Crystallization Behavior ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Scanning Calorimetry ◽  
Scanning Electron

A quaternary Ni86Cr7Si4Fe3 amorphous alloy was synthesized by melt spinning technique. Surface modification was done by electron beam melting (EBM), neutron irradiation and γ-rays. Microstructure of as cast, annealed and modified samples was examined by scanning electron microscope. Crystallization behavior was studied by annealing the samples in vacuum at different temperatures in the range 773-1073 K. Techniques of X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for characterization. Differential scanning calorimetry (DSC) was conducted at various heating rates in the range 10-40 K/min. Thermal parameters like glass transition temperature Tg, crystallization temperature Tx, supercooled liquid region ΔTx and reduced glass transition temperature Trg were measured. The Ni86Cr7Si4Fe3 alloy exhibits wide supercooled liquid region of 60 K indicating good thermal stability. The activation energy was calculated to be 160±4 kJ/mol using Kissinger and Ozawa equations respectively which indicates high resistance against crystallization. The XRD results of the samples annealed at 773 K, 923 K, 973 K and 1073 K/20 min show nucleation of Ni2Cr3 and NiCrFe crystalline phases. Vickers microhardness of the as cast ribbon was measured to be 680.. About 30-50 % increase in hardness was achieved by applying EBM technique.

scholarly journals Effects of Annealing on Enthalpy Recovery and Nanomechanical Behaviors of a La-Based Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 579
Author(s):  
Ting Shi ◽  
Lanping Huang ◽  
Song Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Nanoindentation Measurement

Structural relaxation and nanomechanical behaviors of La65Al14Ni5Co5Cu9.2Ag1.8 bulk metallic glass (BMG) with a low glass transition temperature during annealing have been investigated by calorimetry and nanoindentation measurement. The enthalpy release of this metallic glass is deduced by annealing near glass transition. When annealed below glass transition temperature for 5 min, the recovered enthalpy increases with annealing temperature and reaches the maximum value at 403 K. After annealed in supercooled liquid region, the recovered enthalpy obviously decreases. For a given annealing at 393 K, the relaxation behaviors of La-based BMG can be well described by the Kohlrausch-Williams-Watts (KWW) function. The hardness, Young’s modulus, and serrated flow are sensitive to structural relaxation of this metallic glass, which can be well explained by the theory of solid-like region and liquid-like region. The decrease of ductility and the enhancement of homogeneity can be ascribed to the transformation from liquid-like region into solid-like region and the reduction of the shear transition zone (STZ).

scholarly journals Mechanically Alloyed Amorphous Ti50(Cu0.45Ni0.55)44–xAlxSi4B2 Alloys with Supercooled Liquid Region

2002 ◽  
Vol 17 (7) ◽  
pp. 1743-1749 ◽  
Author(s):  
L. C. Zhang ◽  
J. Xu ◽  
E. Ma
Keyword(s):  
Amorphous Alloys ◽  
Supercooled Liquid ◽  
High Energy ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Beneficial Effects ◽  
State Process ◽  
Transmission Electron

A high-energy ball milling procedure has been developed to produce amorphous alloys in Ti50(Cu0.45Ni0.55)44−xAlxSi4B2 (x= 0, 4, 8, 12) powder mixtures. The milling products were characterized using x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The Ti-based amorphous alloy powders prepared through this solid-state process exhibit a well-defined glass transition and a supercooled liquid region (ΔTx =64 K) close to the largest achieved so far for Ti-based undercooled melts. The substitution of Al for Cu and Ni has beneficial effects on stabilizing the supercooled liquid. Residual nanocrystals of the αTi structure are uniformly dispersed in the amorphous matrix. The composite alloy powders offer the potential for consolidation in the supercooled liquid region to bulk lightweight amorphous alloys and the possibility to attain desirable mechanical properties.

Comments on “Fabrication of ternary Mg–Cu–Gd bulk metallic glass with high glass-forming ability under air atmosphere” [H. Men and D.H. Kim, J. Mater. Res. 18, 1502 (2003)]

2004 ◽  
Vol 19 (2) ◽  
pp. 427-428 ◽  
Author(s):  
Z.P. Lu ◽  
C.T. Liu
Keyword(s):  
Glass Transition ◽  
Metallic Glasses ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Glass Forming Ability ◽  
Bulk Amorphous Alloy ◽  
Liquid Region ◽  
Glass Forming ◽  
Air Atmosphere ◽  
Acta Mater

A new Mg-based bulk amorphous alloy (i.e., Mg65Cu25Gd10) has successfully been developed by Men and Kim [H. Men and D.H. Kim, J. Mater. Res. 18, 1502 (2003)]. They showed that this alloy exhibits significantly improved glass-forming ability (GFA) in comparison with Mg65Cu25Y10 alloy. However, this improved GFA cannot be indicated by the supercooled liquid region ΔT and the reduced glass-transition temperature Trg. As shown in the current comment, the new parameter γ, Tx/(Tg + Tl) defined in our recent papers [Z.P. Lu and C.T. Liu, Acta Mater. 50, 3501 (2002); Z.P. Lu and C.T. Liu, Phys. Rev. Lett. 91, 115505 (2003)] can well gauge GFA for bulk metallic glasses, including the current Mg-based alloys.

Formation of Amorphous and Nanocrystalline Phases in Mechanically Alloyed Zr-, Al-, and Mg-Base Transition Metal Alloys

1994 ◽  
Vol 362 ◽  
Author(s):  
M. Seidel ◽  
J. Eckert ◽  
H.-D. Bauer ◽  
L. Schultz
Keyword(s):  
Transition Metal ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Metal Alloys ◽  
Liquid Region ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Transition Metal Alloys ◽  
Base Transition ◽  
Nanocrystalline Phases

AbstractZr-, Al-, and Mg-base transition metal alloys have been prepared by mechanical alloying and investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Amorphous phases with significant supercooled liquid region form directly during milling from the crystalline starting materials for Zr- and Mg-base alloys. For Albase alloys the formation of mixtures of amorphous and nanocrystalline phases is observed. The results are compared with data for melt-spun and quenched materials. Possible mechanisms for glass formation and crystallization are discussed.

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