Quantitative Crystallization and Nano-Grain Size Distribution Studies of a Fecunbsib Nanocrystalline Alloy

1999 ◽  
Vol 577 ◽  
Author(s):  
M.S. Leu ◽  
T.S. Chin
Keyword(s):  
Grain Size ◽  
Nanocrystalline Alloy ◽  
Soft Magnetic ◽  
Two Phase ◽  
Annealing Conditions ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Crystallization Fraction ◽  
Diffraction Patterns ◽  
Distribution Studies

ABSTRACTSuperior soft magnetic properties of nanocrystalline two-phase FeCuNbSiB alloy can only be attainable from a suitably nano-crystallized structure in the amorphous matrix. In this study a thermal-cycling-annealing process was adopted to anneal the amorphous specimens. The crystallization fraction of Fe73.5Cu1Nb3Si13 5B9 ribbons after different annealing was quantitatively measured by a DTA method through the integrated crystallization enthalpy from annealed samples versus that of as-cast amorphous specimen. The crystallization fraction was estimated to be 70 % as the specimen was annealed for 550°C×7.63 ks, the optimal annealing condition. Using this method, the crystallization quantity of the crystallized FeCuNbSiB amorphous alloy was accurately estimated and controlled during nano-crystallization processes.Abstact:The nanostructure of the annealed flake were investigated by high resolution TEM. The population of grain size is dominant in the range of 3-9 and 3-11 nm, corresponding to isothermal annealing at 520 and 550 °C, respectively, for 910 s. The average grain size associated with the above two annealing conditions is estimated to be 7 and 8.5 nm, respectively. The portion of nanocrystals with grain size smaller than 10 nm is about 80 % for the annealing at 520°C×910 s and 72 % for the annealing at 550°C×910 s, respectively. However, there is only one α-Fe(Si) phase evidenced in the TEM diffraction patterns.

Dielectric Relaxation in Lanthanide Doped/Based Oxides Used for High-k Layers

2014 ◽  
Vol 1024 ◽  
pp. 331-334
Author(s):  
Ce Zhou Zhao ◽  
Stephen Taylor ◽  
Chun Zhao ◽  
Paul R. Chalker
Keyword(s):  
Grain Size ◽  
Dielectric Relaxation ◽  
Chemical Vapor ◽  
Frequency Dispersion ◽  
Atomic Layer ◽  
Organic Chemical ◽  
Grain Sizes ◽  
Annealing Conditions ◽  
Metal Organic ◽  
Diffraction Patterns

Lanthanide doped/based oxide thin films were deposited by liquid injection metal organic chemical vapor deposition or atomic layer deposition. Frequency dispersion is often found in the capacitance-voltage measurements. After taking the extrinsic frequency dispersion into account, the frequency dependence of the dielectric constant (k-value), that is the intrinsic frequency dispersion (dielectric relaxation) has been successfully theoretically modeled. For the physical mechanism of the dielectric relaxation, it was found that the effect of grain sizes for the high-kmaterials structure mainly originates from higher surface stress in smaller grain due to its higher concentration of grain boundary. Variations in the grain sizes of the samples are governed by the deposition and annealing conditions and have been estimated using a range of techniques including Scherrer analysis of the X-ray diffraction patterns. The relationship extracted between grain size and dielectric relaxation suggests that tuning properties for improved frequency dispersion can be achieved by controlling grain size, hence, the strain at the nanoscale dimensions.

Hardness of thin Films of Nanocrystalline Silver and Nickel Composites Studied by Nanoindentation and Finite Element Analysis

1995 ◽  
Vol 400 ◽  
Author(s):  
Boqin Qiu ◽  
Yang-Tse Cheng ◽  
James P. Blanchard
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Finite Element ◽  
Two Phase ◽  
Element Analysis ◽  
Gas Condensation ◽  
Nano Crystalline ◽  
Average Grain Size ◽  
Nickel Composites ◽  
Xrd And Tem

AbstractWhile gas condensation and mechanical alloying have been used to produce nano-phase powders, an effective method of applying these powders as coatings is still lacking. Furthermore, fundamental studies of the mechanical properties of nano-phase powders may be complicated by the porosity associated with consolidation processes. Recently, we have made nano-crystalline composite thin films of Ag-Mo and Ag-Ni by depositing two immiscible elements simultaneous onto substrates. We found, using XRD and TEM, that the average grain size varies from 10 to 100 nm by choosing an appropriate substrate temperature. Nanoindentation measurements showed the hardness of the composite is increased four times by reducing the grain-size of both phases from 100 to 10 nm. The load vs. displacement curves were simulated using a finite element method (ABAQUS). A relationship between the hardness of the two-phase composite and the yield strength of each phase is obtained.

scholarly journals Numerical and Experimental Study on Microstructure Evolution of Ti-6Al-4V Alloy Shaft Perform in Cross-Wedge Rolling Process

2021 ◽  
Author(s):  
Jiayao Yuan ◽  
Xing Chen ◽  
Zhilong Zhao ◽  
Baoshou Sun ◽  
Xuedao Shu
Keyword(s):  
Grain Size ◽  
Microstructure Evolution ◽  
Phase Region ◽  
Rolling Temperature ◽  
Structure Evolution ◽  
Cross Wedge Rolling ◽  
Two Phase ◽  
Rotating Speed ◽  
Area Reduction ◽  
Average Grain Size

Abstract To seek a fundamental understanding for further improving the Ti-6Al-4V alloy utilization of Cross-Wedge Rolling (CWR) and the comprehensive mechanical properties of shaft parts, the effect of the CWR processing parameters on the microstructure evolution of Ti-6Al-4V alloy shaft preform is studied in this paper. An Arrhenius-type microstructure structure evolution model was employed and implemented into the finite element software DEFORM-3D. The average grain size and dynamic re-crystallization volume fraction distribution in the α+β two-phase region and the β single phase region under different rolling temperature, roller rotating speed and area reduction were analyzed, respectively. It is finding that the area reduction, rolling temperature and roller rotating speed significantly affect the microstructure evolution of Ti-6Al-4V alloy. Meanwhile, the corresponding CWR and Metallographic experiments were conducted to verify the reliability of the FE simulation results. Results showed that the agreement of the process parameters effect on dynamic recrystallization in the α+β two-phase region between simulation and experimental is reasonably good. The difference in average grain size in the β phase region between simulation and experimental is ranged from 5.77% to 18.56%. In addition, the evenly distributed microstructure can be found as the area reduction of 50%, rolling temperature of 950℃ and the speed of 5 r⋅min−1 were employed. After rolling under optimized processing conditions, the tensile strength of Ti-6Al-4V alloy shaft preform increased by 18.57% and the plasticity enhanced significantly due to smaller grain size and bi-model microstructure obtained.

scholarly journals The influence of boron doping in the growth of ultra/nanocrystalline diamond films

2012 ◽  
Vol 1395 ◽  
Author(s):  
Fernando A. Souza ◽  
Adriana F. Azevedo ◽  
Maurício R. Baldan ◽  
Neidenêi G. Ferreira
Keyword(s):  
Grain Size ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Columnar Structure ◽  
Nanocrystalline Diamond ◽  
Nanocrystalline Diamond Films ◽  
Average Grain Size ◽  
Diffraction Patterns ◽  
Boron Source ◽  
Boron Dopant

ABSTRACTBoron-doped nanocrystalline diamond (BDND) films were grown on silicon substrates by hot filament chemical vapor deposition in Ar/H2/CH4 gas mixtures. The boron source was obtained from an additional H2 line passing through a bubbler containing B2O3 dissolved in methanol with different B/C ratios. The transition from ultrananocrystalline to nanocrystalline diamond films is clearly shown by the addition of boron dopant to the growth gas mixture. The morphology and structure of these films have markedly different properties. The top view and the cross section of the films were characterized by scanning electron microscopy showing the transition from ultrananocrystalline growth (renucleation process) to a columnar structure of NCD films. Finally, the grain size was obtained from X-ray diffraction patterns of the films. The diamond average grain size increased from 10 to 35 nm for films with 2000 and 30,000 ppm B/C, respectively.

Microstructure and Magnetic Properties of Nd4.5Fe(76.5-x)B18.5Cu0.5Zrx Nanocomposite Permanent Magnetic Alloys

2007 ◽  
Vol 121-123 ◽  
pp. 1277-1280 ◽  
Author(s):  
Y. Qiao ◽  
Mao Cai Zhang ◽  
J. Zhu
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Exchange Coupling ◽  
High Performance ◽  
Magnetic Phase ◽  
Soft Magnetic ◽  
Phase Component ◽  
Average Grain Size ◽  
The Difference ◽  
Microstructure And Magnetic Properties

Nanocomposite Nd2Fe14B/Fe3B magnetic materials with high performance have been obtained by crystallizing over-quenched ribbons. The effect of addition element of Cu and Zr on the phase component, microstructure and magnetic properties of Nd4.5Fe（76.5-x）B18.5Cu0.5Zrx (x= 0.4, 0.5, 1.5, 2.0, 3.0, 4.0) has been systematically investigated. The average grain size of Nd2Fe14B phase and Fe3B phase for the different compositions were calculated from X-day diffraction pattern, which are in accordance with TEM micrographs. For the Nd4.5Fe77B18.5 ribbons, the average grain size of Nd2Fe14B and Fe3B were 34.2 nm and 51.7 nm, and for the Nd4.5Fe76.3B18.5Cu0.5Zr0.4 ribbons, they were only 36.5 nm and 37.1 nm, respectively. It has been found that the additions of Cu and Zr cause the reduction of the difference of grain size between the hard magnetic phase and the soft magnetic phase, that increase the exchange coupling between them. Therefore, it would lead to the magnetic properties improvement. It has been determined that Nd4.5Fe76.3B18.5Cu0.5Zr0.4 was the optimal composition, and the optimal magnetic properties were: Br= 1.204 T, Hci= 271 kA/m, and (BH)max =111.2 kJ/m3.

Effects of Two-Step Annealing on the Magnetic Properties of Iron-Based Nanocrystalline Soft Magnetic Material

2011 ◽  
Vol 688 ◽  
pp. 353-357
Author(s):  
Qiang Song ◽  
Shu Qing Qin
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Crystalline Phase ◽  
Rate Increase ◽  
Nanocrystalline Alloy ◽  
Second Step ◽  
Soft Magnetic Properties ◽  
Soft Magnetic ◽  
One Step ◽  
Phase Nucleation

In the present paper, the effects of two-step annealing on the soft magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 melt spun ribbons were studied. The two-step annealing comprises low-temperature preannealing (first step) for an α-Fe(Si) phase nucleation in an amorphous matrix, and a subsequent high-temperature annealing (second step) for the growth of precipitated crystallites. Compared with a nanocrystalline alloy obtained by conventional one-step annealing at 550 °C for 1 h, the grain size of α-Fe（Si）crystalline phase in the Fe73.5Cu1Nb3Si13.5B9 alloy decreased greatly after it is pre-annealed at 480°C for 1 h followed by annealing at 550°C for 40 min. It has been shown that the soft magnetic properties can be significantly improved by applying two-step annealing. The decrease of grain size of α-Fe(Si) crystalline phase may result from the nucleation rate increase during the crystallization of pre-annealed.

Effect of Annealing Conditions on the Grain Size of Nanocrystalline Copper Thin Films

2008 ◽  
Vol 587-588 ◽  
pp. 483-487 ◽  
Author(s):  
Sonia Simões ◽  
Rosa Calinas ◽  
P.J. Ferreira ◽  
M. Teresa Vieira ◽  
Filomena Viana ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Grain Size ◽  
Grain Growth ◽  
Copper Substrate ◽  
Nanocrystalline Metals ◽  
Nanocrystalline Copper ◽  
Annealing Conditions ◽  
Transmission Electron ◽  
Average Grain Size

Nanocrystalline metals demonstrate a broad range of fascinating mechanical properties at the nanoscale, namely a significant increase in hardness and superior yield stress. In this regard, understanding grain growth in nanocrystalline metals is crucial, particularly because nano size grains are characterized by a high curvature, which results in a high driving force for grain growth. In this work, the effect of annealing conditions on grain size of copper nanocrystalline thin films was investigated. The nanocrystalline copper thin films were first deposited by d.c. magnetron sputtering on a copper substrate. The specimens were then annealed in vacuum at 100, 300 and 500°C from 10 minutes to 5 hours. Transmission electron microscopy observations revealed that the as-deposited thin films have a bimodal grain size distribution; an average grain size of 43±2nm and the presence of nanotwins. Abnormal grain growth was observed for some samples annealed. Increasing the annealing time induced significant grain growth and promoted twin formation in the larger grains. Finally, the hardness of these nanocrystalline Cu thin films was determined using atomic force microscope. The relation between mechanical properties, annealing conditions and grain size was analyzed.

Structure and Magneto-Resistance in Nanostructured Sr2Fe1-xCrxMoO6 (0≤x≤0.3) Double Perovskite Componds

2011 ◽  
Vol 130-134 ◽  
pp. 3298-3301
Author(s):  
Xiang Hu Li ◽  
Dan Li
Keyword(s):  
Grain Size ◽  
Sol Gel ◽  
Double Perovskite ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
X Ray ◽  
Average Grain Size ◽  
Diffraction Patterns ◽  
Magneto Resistance ◽  
Fe Substitution

The compounds of Fe substitution of Cr in nanotructured Sr2Fe1-xCrxMoO6(0≤x≤0.3) double perovskite have been prepared by sol-gel method. The x-ray diffraction patterns of the samples show that the samples are in nanometer range. And the average grain size D for these samples is 39.7, 37.1, 33.4, 31.9, and 31.2nm, respectively, decreases with the increasing of Cr ion. The saturation magnetization and the magnetoresistance of the samples decrease with the increasing of Cr for the disorder defects which increase for the close ionic radii of Mo and Cr.

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