The activation energy and kinetic of the nanocrystallization process of Al 85 Ni 9 Nd 4 Co 2 amorphous alloy

2009 ◽  
Author(s):  
V.A. Serban ◽  
C. Codrean ◽  
C. Opris ◽  
D. Utu ◽  
M. Lita
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy

Non—Isothermal Differential Scanning Calorimetry Studies on Nanocrystallization Kinetics of Fe81Si3.5B13.5C2 Amorphous Alloy

2011 ◽  
Vol 688 ◽  
pp. 180-185
Author(s):  
Yu Zhang ◽  
Wei Lu ◽  
Biao Yan ◽  
Yu Xin Wang ◽  
Ying Yang
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Amorphous Alloy ◽  
Three Dimensional ◽  
Crystallization Mechanism ◽  
Scanning Calorimetry ◽  
Average Value ◽  
Initial Stage ◽  
Friedman Method ◽  
Kinetics Of

The nanocrystallization kinetics of the Fe81Si3.5B13.5C2amorphous alloy was investigated by differential scanning calorimetry (DSC). The apparent activation energy Ea, as well as the nucleation and growth kinetic parameters has been calculated by Kissinger and Ozawa methods. The changeable activation energy Eawith crystalline fraction α was obtained by the expended Friedman method without assuming the kinetic model function, and the average value of Eawas 364±20 kJ/mol. It was shown that the crystallization mechanism of initial stage (0<α<0.7) of the transformation was bulk crystallization with two and three dimensional nucleation graining growth which was controlled by diffusion. For the middle stage (0.7<α<0.9), the crystallization mechanism is surface crystallization with one dimensional nucleation graining growth at a near-zero nucleation rate. In the final stage(α>0.9)，the local Avrami exponents rose anomalously from 1.4 to about 2.0.

Ti50Fe25Ni25 Amorphous Alloy Prepared by Mechanical Alloying

2011 ◽  
Vol 327 ◽  
pp. 76-80
Author(s):  
Yu Ying Zhu ◽  
Qiang Li ◽  
Yun Hua He ◽  
Ge Wang ◽  
Xing Hua Wang
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Mechanical Alloying ◽  
High Energy ◽  
Structural Features ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Crystallization Peak ◽  
Activation Energy Of Crystallization ◽  
Amorphous Alloy Powder

A new ternary Ti-based amorphous alloy, Ti50Fe25Ni25, is prepared by the mechanical alloying. The milling is performed in a high-energy planetary ball mill under argon atmosphere. Fully Ti50Fe25Ni25amorphous alloy powder is obtained after milled 160h. The milling speed is 300rpm and the weighs ratio of ball to powder is 10:1. The structural features are studied by X-ray diffraction and field emission scanning electron microscope, and the thermal stability is investigated by a differential scanning calorimeter. The super-cooled liquid region of the amorphous alloy increases from 98K to 119K as the heating rate increasing from 10K/min to 40K/min. The effective activation energy of crystallization is estimated with modified Kissinger’s plot. The initial crystallization activation energyEx1and the first crystallization peakEp1are 155.9KJ/mol and 188.5KJ/mol, respectively.

Kinetics Study on Non-Isothermal Crystallization of Amorphous Alloy Mg65Cu15Ag10Y10

2011 ◽  
Vol 413 ◽  
pp. 432-438
Author(s):  
Xiao Jun Wang ◽  
Tian Dong Xia ◽  
Xue Ding Chen
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Heating Rate ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Continuous Heating ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Local Activation ◽  
Local Activation Energy

The crystallization kinetics of amorphous alloy Mg65Cu15Ag10Y10has been studied by differential scanning calorimetry in the mode of continuous heating annealing. It is found that both DSC curves and activation energy show a strong dependence on the heating rate. The activation energy for crystallization are determined as 186.1 and 184.4 KJ mol−1for the heating rates β=5-20 Kmin−1, and 107.5 and 110.0 KJmol−1for the heating rates β=20-80Kmin−1, when using the Kissinger equation and the Ozawa equation, respectively. Local activation energy at any volume fraction crystallized was obtained by the general Ozawa's isoconversional method. The average value of local activation energy for heating rates ranging from 5 to 20Kmin−1is 180.9 KJ mol−1and for heating rates ranging between 20 and 80Kmin−1is 110.2 KJ mol−1. Using the Suriñach curve fitting procedure, the kinetics mode was specified. The JMA kinetics is manifested as a rule in the early stages of the crystallization. The JMA exponent,n, initially being larger than 4 and continuously decreases to about 2 along with the development of crystallization. The NGG-like mode dominates in the advanced stages of the transformation. These two modes are mutually independent. The proportion between the JMA-like and the NGG-like modes is related to the heating rate.

A correlation method for determination of crystallization mechanism and activation energy of amorphous alloy

1998 ◽  
Vol 29 (1) ◽  
pp. 149-151 ◽  
Author(s):  
Dejiu Shen ◽  
Yulin Wang ◽  
Guanzhong Xing ◽  
Liyang Li ◽  
Zhongyi Shen
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Correlation Method ◽  
Crystallization Mechanism

scholarly journals Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

2015 ◽  
Vol 60 (2) ◽  
pp. 1543-1546 ◽  
Author(s):  
J. Guo ◽  
X. Hu ◽  
J. Liu ◽  
T. Feng ◽  
E.Y. Yoon ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Amorphous Alloy ◽  
Viscous Flow ◽  
Amorphous Alloys ◽  
Materials Science ◽  
Onset Temperature ◽  
Superheated Liquid ◽  
Liquid Region ◽  
Liquid Fragility

Abstract Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

scholarly journals Reduction and Immobilization of Movable Cu2+ Ions in Soils by Fe78Si9B13 Amorphous Alloy

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 310
Author(s):  
Liefei Pei ◽  
Xiangyun Zhang ◽  
Zizhou Yuan
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Apparent Activation Energy ◽  
Magnetic Separation ◽  
Dynamic Process ◽  
Contaminated Soils ◽  
Iron Hydroxide ◽  
Reaction Rate Constant ◽  
Reaction Products ◽  
Soil System

The Fe-based amorphous alloy (Fe78Si9B13AP) is applied to the remediation of copper contaminated soil for the first time. The dynamic process of conversion of movable Cu to immobilized forms in the soil system is analyzed. In addition, the dynamic process of form transformation of Cu2+ ions in the soil system is analyzed. The morphology and phase composition of the reaction products are characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Finally, the feasibility of recovering residual stabilizer particles and attached immobilized copper by the magnetic separation process is discussed. The results show that the apparent reaction rate constant of Fe79Si9B13AP with Cu2+ ions is higher than that of zero valent iron (ZVI) at all the experimental temperatures. According to the Arrhenius formula, the apparent activation energy of the reaction of Fe78Si9B13AP and ZVI with Cu2+ ions is 13.24 and 19.02 kJ/mol, respectively, which is controlled by the diffusion process. The lower apparent activation energy is one of the important reasons for the high reaction activity of Fe78Si9B13AP. After 7 days of reaction, a continuous extraction of the experimental soil shows that the main form of copper in the immobilized soil is Cu and copper combined with iron (hydroxide) oxide, and there is almost no soluble copper with a strong mobility, which effectively reduced the bioavailability of copper in the soil. The magnetic separation results of the treated soil show that the recovery rates of immobilized copper in Fe78Si9B13AP and soil are 47.23% and 21.56%, respectively, which reduced the content of iron and copper in the soil to a certain extent. The above experimental results show that Fe78Si9B13AP is a promising new material for the remediation of heavy metal contaminated soils, and provides more new references for the application of amorphous alloys in the field of remediation of water and soil contaminated by heavy metals and organic matter.

scholarly journals Influence of structural changes on electrical and magnetic properties of the Co84Fe5,3Si8,5B2,2 amorphous alloy

2005 ◽  
Vol 37 (3) ◽  
pp. 231-235 ◽  
Author(s):  
S.R. Djukic ◽  
Radojko Simeunovic ◽  
Aleksa Maricic
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Relaxation Process ◽  
Structural Changes ◽  
Crystallization Process ◽  
State Density ◽  
Annealing Process ◽  
Scanning Calorimetry ◽  
Electrical And Magnetic Properties ◽  
Electronic State Density

The crystallization process of the Co84Fe5.3Si8.5B2.2 amorphous alloy examined by differential scanning calorimetry (DSC) exhibits three exothermal steps at Tcr1=649K, Tcr2=800K, and Tcr3=838K. The rate constants of the first relaxation process (determined at 598K and 623K) are k1=5*10-4 s and k2=8*10-4 s and the corresponding activation energy Ea1=26.23 kJ/mol. The data for the relaxation process before the second crystallization step (determined at 683K and 713K) are k3=14.5*10-4 s and k4=17.5*10-4 s and the corresponding activation energy Ea2=60.0 kJ/mol. The process of structural relaxation in non-isothermal and isothermal conditions was studied by analysis of the results of measurements of the thermo electromotive force (TEMF). From the change of the temperature coefficient of TEMF that follows each annealing process, the relative electronic state density changes at the Fermi level were determined: ?N21/N2=5,45%, ?N22/N2=5,76%, ?N23/N2=7,57% and ?N24/N2=9,85%.

Crystallization Kinetics of Ti50Fe22Ni22Sn6 Amorphous Powders

2011 ◽  
Vol 108 ◽  
pp. 12-17
Author(s):  
Yu Ying Zhu ◽  
Qiang Li ◽  
Yun Hua He ◽  
Ge Wang ◽  
Xing Hua Wang
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Crystallization Kinetics ◽  
Crystallization Process ◽  
Amorphous Powder ◽  
High Energy ◽  
Liquid Region ◽  
Amorphous Powders ◽  
Kinetics Of ◽  
Dsc Curves

The Ti50Fe22Ni22Sn6 amorphous powder was prepared by mechanical alloying with a high-energy planetary ball mill. Crystallization kinetics of the milled amorphous powders was investigated by DSC. Thermal analysis showed that when the heating rate increasing from 10K/min to 40K/min, the super-cooled liquid region of milled amorphous alloy increased from 93K to 110K. On the basis of the obtained DSC curves, the characteristic temperatures of the amorphous powders could be measured. The equations of Kissinger and Ozawa were used to calculate the crystallization activation energies of the milled amorphous alloy for comparing. The activation energy for the glass transition Eg had the maximum values of 650KJ/mol and 629KJ/mol calculated from Kissinger and Ozawa, respectively. In addition, the second crystallization process had a higher activation energy value comparing with the others crystallization events.

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