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.

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.

Formation of Ni57Zr20Ti22Pb1 Amorphous Powders by Mechanical Alloying

2007 ◽  
Vol 539-543 ◽  
pp. 2767-2772
Author(s):  
Pee Yew Lee ◽  
S.S. Hung ◽  
Jason S.C. Jang ◽  
Giin Shan Chen
Keyword(s):  
Thermal Stability ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Atomic Size ◽  
X Ray ◽  
Amorphous Powders ◽  
Thermal Stability Of

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.

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.

Refractory Mo–Si-Based Glassy Alloy Designed for Ultrahigh Strength and Thermal Stability

2005 ◽  
Vol 20 (11) ◽  
pp. 2910-2913 ◽  
Author(s):  
X.Q. Zhang ◽  
W. Wang ◽  
E. Ma ◽  
J. Xu
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Metallic Glasses ◽  
Glassy Alloy ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
High Glass Transition Temperature ◽  
Mechanically Alloyed ◽  
Ultrahigh Strength

Mechanically alloyed Mo44Si26Ta5Zr5Fe3Co12Y5 multicomponent glassy alloy exhibits an exceptionally high glass transition temperature of 1202 K and a crystallization temperature of 1324 K, as well as an ultrahigh hardness of 18 GPa. This example is used to demonstrate metallic glasses that possess extraordinary thermal stability and ultrahigh strength and, at the same time, a wide supercooled liquid region (122 K) that is needed for processing into bulk forms through powder metallurgy routes.

Amorphization Behavior of Ni57Zr20Ti22Ge1 Powders by Mechanical Alloying

2011 ◽  
Vol 479 ◽  
pp. 48-53
Author(s):  
Kai Chen Kuo ◽  
Pee Yew Lee ◽  
Jai Yush Yen
Keyword(s):  
Thermal Stability ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Atomic Size ◽  
X Ray ◽  
Amorphous Powders ◽  
Thermal Stability Of

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Ge1 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 Ni57Zr20Ti22Ge1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 761 K and 839 K, respectively. The supercooled liquid region ΔT is 78 K. The appearance of wide supercooled liquid region may be mainly due to the Ge additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Ge1 powders.

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.

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.

Glass-forming ability and thermal stability of Fe62Nb8−xZrxB30 and Fe72Zr8B20 amorphous alloys?

Open Physics ◽  
2004 ◽  
Vol 2 (1) ◽  
Author(s):  
M. Shapaan ◽  
J. Lábár ◽  
L. Varga ◽  
J. Lendvai
Keyword(s):  
Thermal Stability ◽  
Amorphous Alloys ◽  
Strong Dependence ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Glass Forming Ability ◽  
Partial Replacement ◽  
Liquid Region ◽  
Glass Forming ◽  
Thermal Stability Of

AbstractGlass-forming ability (GFA) and thermal stability of Fe62Nb8B30, Fe62Nb6Zr2B30 and Fe72Zr8B20 at % amorphous alloys were investigated by calorimetric (DSC and DTA) measurements. The crystallization kinetics was studied by DSC in the mode of continuous versus linear heating and it was found that both the glass transition temperature, Tg, and the crystallization peak temperature, Tp, display strong dependence on the heating rate. The partial replacement of Nb by Zr leads to lower Tg and Tx temperatures and causes a decrease of the supercooled liquid region. JMA analysis of isothermal transformation data measured between Tg and Tx suggests that the crystallization of the Fe62Nb8B30 and Fe62Nb6Zr2B30 amorphous alloys take place by three-dimensional growth with constant nucleation rate. Nb enhances the precipitation of the metastable Fe23B6 phase and stabilizes it up to the third crystallization stage. Zr addition increases the lattice constant of Fe23B6 and, at the same time, decreases the grain size.

Solid-state synthesis of new glassy Co65Ti20W15 alloy powders and subsequent densification into a fully dense bulk glass

2005 ◽  
Vol 20 (10) ◽  
pp. 2845-2853 ◽  
Author(s):  
M. Sherif El-Eskandarany ◽  
M. Omori ◽  
A. Inoue
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Glassy Alloy ◽  
Supercooled Liquid ◽  
High Energy ◽  
Supercooled Liquid Region ◽  
Exothermic Peak ◽  
Liquid Region ◽  
Plasma Sintering

The mechanical alloying method was used to synthesize a single glassy phase of Co65Ti20W15 alloy powders, using a high-energy ball mill. The glass transition temperature of the end-product, which was obtained after 173 ks of milling time, lies at 786 K, whereas the crystallization takes place at 878 K through a single sharp exothermic peak with an enthalpy change of crystallization of −4.37 kJ/mol. The reduced glass transition temperature was found to be 0.51. This glassy alloy powders exhibit a very large supercooled liquid region (92 K) for a ternary metallic system. The spark plasma sintering method was used to consolidate the glassy powders under an argon gas atmosphere at 843 K with a pressure of 19.6–38.2 MPa. The sample that was consolidated within 180 s maintains its chemically homogeneous glassy structure with a relative density of above 99.6%. Neither the supercooled liquid region nor crystallization temperature was affected by such a rapid consolidation procedure. Thus, the thermal stability of the bulk glassy sample is almost identical with the original glassy powders. The Vickers microhardness of the bulk glassy Co65Ti20W15 reveals high values, ranging between 8.69 and 8.83 GPa. The fabricated bulk glassy alloy shows high compressive strength of 2.44 GPa with a Young’s modulus of 176.81 GPa. Neither yielding stress, nor plastic strain could be detected for this glassy alloy, which its elastic strain is 1.33%.

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