Formation, Mechanical and Electrical Properties of Ni-based Amorphous alloys and their Nanocrystalline Structure

2002 ◽  
Vol 740 ◽  
Author(s):  
Xiangcheng Sun ◽  
Tiemin Zhao
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Alloy ◽  
Amorphous Alloys ◽  
Interaction Model ◽  
Nanocrystalline Structure ◽  
Primary Crystallization ◽  
Electron Interaction ◽  
Liquid Region

ABSTRACTA Ni-based amorphous alloy in Ni60Ti20Zr20 system was prepared by melting spinning. The glass transition temperature (Tg) was as high as about 760 K, the supercooled liquid region was quite wide, ΔTx = 50 K (ΔTx= Tx-Tg, Tx crystallization temperature), and the reduced glass transition temperature (Tg/Tm) was 0.60. The amorphous alloys exhibited a high tensile strength (of= 1015 MPa) at room temperature. The electrical conductivity obeyed a T12 law over the range of 15 K< T < 300 K, which can be explained by an electron-electron interaction model. After annealing the amorphous alloy into primary crystallization, a nanocomposites consisted of metastable Ti2Ni and Zr2Ni nanophases with size less than 15 nm embedded in the amorphous matrix was appeared.

NANOSTRUCTURED AND BULK AMORPHOUS Zr-BASED ALLOYS PREPARED BY MECHANICAL ALLOYING AND ARC MELTING

2003 ◽  
Vol 17 (10) ◽  
pp. 2035-2044 ◽  
Author(s):  
S. BASKOUTAS ◽  
P. LEMIS-PETROPOULOS ◽  
V. KAPAKLIS ◽  
Y. KOVEOS ◽  
C. POLITIS
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mechanical Alloying ◽  
Amorphous Alloys ◽  
Liquid Region ◽  
X Ray ◽  
Bulk Amorphous Alloys ◽  
Arc Melting ◽  
Amorphous Powders

We have produced powders of nanostructured and amorphous alloys as well as bulk amorphous alloys with composition Zr 64 Cu 18 Ni 10 Al 8 by mechanical alloying and by quenching arc melted melts in water cooled cooper dies, respectively. The alloys were investigated by X-ray diffraction as well as by thermal analysis in order to determine the structure and thermal properties. The mechanical alloyed amorphous powders and bulk amorphous cylinders show the same thermal and X-ray characteristics. For the amorphous powders, we find that the glass transition temperature Tg is 657 K and the crystallization temperature Tx is 752 K. For bulk amorphous alloys with the same composition prepard by arc melting and liquid quenching Tgis 655 K and the Tx is 725 K. Moreover for the bulk amorphous alloys the supercooled liquid region Δ Txg is 70 K, the reduced glass transition temperature tg is 0.557, the Lu–Liu parameter γ which represents the glass forming ability for bulk metallic glasses is 0.396 and experimentally the critical cooling rate Rc takes the value 7 K s -1.

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).

An Experimental Study for Crystallization Characteristics of Nd-Based Alloy

2011 ◽  
Vol 268-270 ◽  
pp. 611-615
Author(s):  
Feng Yang ◽  
Zhi Hua Gao ◽  
Di Wang ◽  
Yang Liu
Keyword(s):  
Experimental Study ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Heating Temperature ◽  
Liquid Region ◽  
Magnetic Alloys ◽  
Ordinary Temperature ◽  
Transition Temperature Increase

The bulk metallic glass has received much attention from scientist and engineer. In this paper, we fabricated metallic glass of Nd-based and carried out experimental research. This kind of metallic glass has shown a distinct glass transition and stable super-cooled liquid region. At the same time, we find the paramagnetic performance of Nd-based metallic glass is different from other hard magnetic alloys at ordinary temperature. The DSC experiment indicate that the glass transition temperature increase with the heating temperature.

Hot pressing and characterizations of mechanically alloyed Zr52Al6Ni8Cu14W20 glassy powders.

2006 ◽  
Vol 21 (4) ◽  
pp. 976-987 ◽  
Author(s):  
M. Sherif El-Eskandarany ◽  
A. Inoue
Keyword(s):  
Solid Solution ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
Liquid Region ◽  
Gradual Change

Low-energy ball milling technique was successfully used to synthesis new glassy Zr52Al6Ni8Cu14W20 multicomponent alloy powders using mechanical alloying method. During the intermediate stage of milling the atoms of Zr, Al, Ni, and Cu migrated and diffused into the W lattice to form a body-centered cubic solid solution phase. As the milling time increases, the obtained metastable powders are subsequently subjected to continuous defects and lattice imperfections that lead to a gradual change in the free energy so that solid solution phase transformed to another metastable phase (glassy). The glassy powders that were obtained after 720 ks milling are fully amorphous and have spherical-like morphology with an average particle size of 0.60 μm in diameter. The synthetic glassy Zr52Al6Ni8Cu14W20 alloy powder, which exhibits a glass transition temperature of 811 K, crystallizes at a high temperature (884 K) through a single sharp exothermic peak with an enthalpy change of crystallization of −5.48 kJ/mol. Whereas the supercooled liquid region before crystallization of the obtained glassy powders is 73 K, the reduced glass transition temperature (ratio between Tg and liquidus temperatures) was found to be 0.46. The fabricated glassy powders were consequently hot-pressed into bulk samples in an argon gas atmosphere at several temperatures with a pressure of 936 MPa. The samples that were consolidated within the temperature of the supercooled liquid region are fully dense, with relative density above ∼99.82%, and maintain their original homogeneous glassy structure. They have high Vickers microhardness values in the range between 8.46 and 8.62 GPa. They also show very high fracture strength (2.13 GPa) with an extraordinary high Young's modulus of 138 GPa. Neither yielding stress, nor plastic strain could be detected for this glassy alloy, the elastic strain of which is 1.47%.

Isothermal Crystallization of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy Near the Glass Transition Temperature

2004 ◽  
Vol 449-452 ◽  
pp. 933-936 ◽  
Author(s):  
Zhuang Qi Hu ◽  
Q.S. Zhang ◽  
Hai Feng Zhang ◽  
B.Z. Ding ◽  
Z.M. Rao
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Alloy ◽  
Amorphous Phase ◽  
Isothermal Crystallization ◽  
Metastable Phases ◽  
Bulk Amorphous Alloy ◽  
Thermal Stability Of

Isothermal crystallization of Zr55Al10Ni5Cu30bulk amorphous alloy near the glass transition temperature has been investigated. The microstructures and thermal stability of the annealed amorphous alloy were examined by HRTEM, XRD and DSC. The amorphous phase in the Zr55Al10Ni5Cu30bulk amorphous alloy crystallized at 420°C through the following processes of amorphous →amorphous with clusters + metastable phases→metastable phases.

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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