THERMODYNAMIC ANALYSIS OF PHASE FORMATION IN MECHANICAL ALLOYED Fe3Al POWDER

2011 ◽  
Vol 18 (03n04) ◽  
pp. 115-120
Author(s):  
L. X. PANG ◽  
X. H. HAO ◽  
N. F. HAN ◽  
J. XU ◽  
X. D. TANG ◽  
...  
Keyword(s):  
Solid Solution ◽  
Driving Force ◽  
Lattice Strain ◽  
Driving Forces ◽  
Phase Evolution ◽  
Mechanically Alloyed ◽  
Energy Of Mixing ◽  
Supersaturated Solid Solutions ◽  
Free Energy Of Mixing ◽  
Aluminum Phase

Nanocrystalline supersaturated solid solutions were formed by mechanically alloyed Fe-28Al (in atom percent) from the elemental powder of iron and aluminum. Phase evolution, grain size and lattice strain of these powders were determined and discussed. A thermodynamic model was developed based on semi-experimental theory of Miedema to calculate the chemical driving force for phase evolution. The influence of thermodynamic driving forces, namely the Gibbs free energy of mixing, for the solid solution and the amorphous was discussed and corresponded to the sequence of phase formations during mechanical alloying.

scholarly journals Microstructural Evolution, Thermodynamics and Kinetics of Mo-Tm2O3 Powder Mixtures during Ball Milling

2016 ◽  
Author(s):  
Yong Luo ◽  
Guang Ran ◽  
Nanjun Chen ◽  
Qiang Shen ◽  
Yaoli Zhang
Keyword(s):  
Solid Solution ◽  
Ball Milling ◽  
Microstructural Evolution ◽  
Driving Force ◽  
Phase Evolution ◽  
Heat Of Mixing ◽  
Powder Mixtures ◽  
Thermodynamics And Kinetics ◽  
Transmission Electron ◽  
Kinetics Of

The microstructural evolution, thermodynamics and kinetics of Mo-21%Tm2O3 (mass fraction, %) powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into Mo crystal. The supersaturated nanocrystalline solid solution of Mo (Tm, O) was obtained after 96 h of ball milling. The elements of Mo, Tm and O were distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo-21%Tm2O3, it was mechanical work, not negative heat of mixing, that provided the driving force to form supersaturated nanocrystalline Mo (Tm, O) solid solution.

Metastable Phase Formation in Mechanically Alloyed Sm-Co-Fe

1997 ◽  
Vol 481 ◽  
Author(s):  
P. A. I. Smith ◽  
J. Ding ◽  
P. G. McCormick ◽  
R. Street
Keyword(s):  
Phase Formation ◽  
Metastable Phase ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Two Phase ◽  
Fe Content ◽  
Energy Of Mixing ◽  
Metastable Phase Formation ◽  
Free Energy Of Mixing ◽  
Bcc Phase

ABSTRACTA detailed phase analysis of mechanically alloyed (Sm0.18Co0.82)100-xFex powders has been performed using X-ray diffraction and Mössbauer spectroscopy. A two-phase structure develops as the Fe content is increased, with an increasing proportion of bcc Fe-Co in addition to amorphous Sm-Co-Fe. Both phases become richer in Fe, but Fe is concentrated in the bcc phase, due to a limited ability of Fe to substitute in amorphous Sm-Co. Changes in phase formation with increasing Fe content can be correlated with changes in the calculated free energy of mixing of amorphous Sm-Co-Fe.

Microstructure and thermodynamic analysis of nanostructured Cu-13.2%Al-4%Ni ternary system synthesized by mechanical alloying

2019 ◽  
Vol 116 (6) ◽  
pp. 628
Author(s):  
Rouzbeh Mayahi ◽  
Ali Shokuhfar ◽  
Mohammad Reza Vaezi
Keyword(s):  
Solid Solution ◽  
Mechanical Alloying ◽  
Crystallite Size ◽  
Amorphous Phase ◽  
Thermodynamic Analysis ◽  
Thermodynamic Data ◽  
Driving Force ◽  
Lattice Strain ◽  
High Energy ◽  
Structural Defects

Thermodynamic analysis of nanostructured Cu-13.2%Al-4%Ni synthesized by mechanical alloying was studied through Miedema’s semi-empirical model. The variations of lattice strain, crystallite size and microstructural evolution at various milling times were also measured using X-ray diffraction and scanning electron microscope. The results showed an increase in lattice strain and reduction in crystallite size due to an increase in density of structural defects as a result of high-energy collisions during mechanical alloying. The calculated thermodynamic data suggested that in all binary Cu-Al, Al-Ni and Ni-Cu systems, there is a driving force for solid solution formation over all compositions due to negative Gibbs free energy changes in those compositions, while this value is positive for the formation of amorphous phase over some compositions which can be attributed to the absence of driving force. Additionally, thermodynamic data were in agreement with XRD results which showed solid solution was formed at middle stages of mechanical alloying. Moreover, it is concluded that the formation of solid solution is easier at three corners of ternary diagram, where the concentration of one element is major, whilst amorphous phase formation is more desirable in other compositions.

Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

1977 ◽  
Vol 35 ◽  
pp. 298-299
Author(s):  
Jordi Marti ◽  
Timothy E. Howson ◽  
David Kratz ◽  
John K. Tien
Keyword(s):  
Solid Solution ◽  
Volume Fraction ◽  
Stress Rupture ◽  
Oxide Dispersion Strengthened ◽  
Solid Solution Alloy ◽  
Oxide Dispersion ◽  
Creep And Stress Rupture ◽  
Mechanically Alloyed ◽  
Fine Microstructure ◽  
Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

Interionic Pair Potential, hard sphere diameter and entropy of mixing of NaCd compound forming binary molten alloys under the framework of Pseudopotential theory

2014 ◽  
Vol 10 (6) ◽  
pp. 2843-2852
Author(s):  
Sujeet Kumar Chatterjee ◽  
Lokesh Chandra Prasad ◽  
Ajaya Bhattarai
Keyword(s):  
Nearest Neighbor ◽  
Effective Interaction ◽  
Pair Potential ◽  
Sphere Diameter ◽  
Compound Formation ◽  
Pseudopotential Theory ◽  
Energy Of Mixing ◽  
Asymmetric Behaviour ◽  
Statistical Mechanical ◽  
Free Energy Of Mixing

The observed asymmetric behaviour of mixing of  NaCd liquid alloys around equiatomic composition with smaller negative values for free energy of mixing at compound forming concentration, i.e. GMXS = -4.9KJ at Ccd =0.66 has  aroused our interest to undertake a theoretical investigation of this system.A simple statistical mechanical theory based on compound formation model has been used to investigate the energetics of formation of intermetallic compound Cd2Na in the melt through the study of entropy of mixing.Besides, the interionic interactions between component atoms Na and Cd of the alloys have been understood through the study of interionic pair potential фij(r), calculated from pseudopotential theory in the light of CF model.Our study of фij(r) suggest that the effective interaction between Na-Na atoms decreases on alloying with Cd atom, being minimum for compound forming alloy( Cd 0.66 Na 0.34 ).The nearest neighbor distance between Na-Na atoms does not alter on alloying. Like wise Na-Na,  effective interaction between  Cd-Cd atom decreases from pure state to NaCd alloys, being smaller at compound forming  concentration Cd 0.66 Na 0.34.The computed values of SM from pseudopotential theory are positive at all concentrations, but the agreement between theory and experimental is not satisfactory. This might be happening due to parameterisation of σ3 and Ψcompound.

scholarly journals Driving forces on dislocations: finite element analysis in the context of the non-singular dislocation theory

2021 ◽  
Author(s):  
Xiandong Zhou ◽  
Christoph Reimuth ◽  
Peter Stein ◽  
Bai-Xiang Xu
Keyword(s):  
Finite Element ◽  
Dislocation Loop ◽  
Driving Force ◽  
Complex Geometry ◽  
Driving Forces ◽  
Singular Solutions ◽  
Dislocation Model ◽  
Configurational Force ◽  
Element Analysis ◽  
Dislocation Configuration

AbstractThis work presents a regularized eigenstrain formulation around the slip plane of dislocations and the resultant non-singular solutions for various dislocation configurations. Moreover, we derive the generalized Eshelby stress tensor of the configurational force theory in the context of the proposed dislocation model. Based on the non-singular finite element solutions and the generalized configurational force formulation, we calculate the driving force on dislocations of various configurations, including single edge/screw dislocation, dislocation loop, interaction between a vacancy dislocation loop and an edge dislocation, as well as a dislocation cluster. The non-singular solutions and the driving force results are well benchmarked for different cases. The proposed formulation and the numerical scheme can be applied to any general dislocation configuration with complex geometry and loading conditions.

Microstructural Study of Thin Films CuFe Obtained by Thermal Evaporation of Nanostructured Milled Powder

2017 ◽  
Vol 47 ◽  
pp. 71-78
Author(s):  
H. Mechri ◽  
Ahmed Haddad ◽  
M. Zergoug ◽  
Mohammed Azzaz
Keyword(s):  
Thin Films ◽  
Solid Solution ◽  
Physical Vapor Deposition ◽  
Thermal Evaporation ◽  
Supersaturated Solid Solution ◽  
Milled Powder ◽  
Mechanically Alloyed ◽  
Glass Substrates ◽  
Milling Duration ◽  
Tungsten Boat

Commercial copper and iron powders were used as starting materials. These powders were mechanically alloyed to obtain Cu(100-x) Fex supersaturated mixture. The milling duration was chosen in such a way as to obtain a nanostructured mixture and to form a supersaturated solid solution of CuFe; the powder mixture was used to deposit CuFe on a glass substrate. The elaboration of our films has been carried out using thermal evaporation process (physical vapor deposition) under 1 × 10-6 mbar vacuum from an electrically heated tungsten boat, using the supersaturated solid solution Cu(100-x) Fex powder obtained by mechanical alloying. The films deposition has been done on glass substrates. In this study, we present the composition effect on the structural and magnetic proprieties of Cu(100-x) Fex powder and thin films. The chemical composition, structural and magnetic proprieties of milled powders and thin films were examined by SEM, TEM, XRD, XRF and VSM.

Higher Order Conditional Probabilities and Thermodynamics of Binary Molten Alloys

1997 ◽  
Vol 11 (02n03) ◽  
pp. 93-106 ◽  
Author(s):  
O. Akinlade
Keyword(s):  
Free Energy ◽  
Experimental Evidence ◽  
Cluster Model ◽  
Excess Free Energy ◽  
Higher Order ◽  
Thermodynamic Quantities ◽  
Equiatomic Composition ◽  
Conditional Probabilities ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing

The recently introduced four atom cluster model is used to obtain higher order conditional probabilities that describe the atomic correlations in some molten binary alloys. Although the excess free energy of mixing for all the systems studied are almost symmetrical about the equiatomic composition, most other thermodynamic quantities are not and thus, the study enables us to explain the subtle differences in their physical characteristics required to describe the mechanism of the observed strong heterocoordination in Au–Zn or homocoordination in Cu–Ni within the same framework. More importantly, we obtain all calculated quantities for the whole concentration range thus complimenting experimental evidence.

Driving forces and structural changes of China as a market provider for Korea

2018 ◽  
Vol 22 (3) ◽  
pp. 194-211 ◽  
Author(s):  
Yongqi Feng ◽  
Tianshu Zhang
Keyword(s):  
Steady State ◽  
Driving Force ◽  
Design Methodology ◽  
Structural Changes ◽  
Driving Forces ◽  
Consumption Expenditure ◽  
Input Output ◽  
Content Type ◽  
Fixed Capital Formation ◽  
The Impact

Purpose The purpose of this paper is to provide a better understanding of the driving forces and structural changes of China as a market provider for Korea. This paper gives the answers for the following questions: How do China’s final demands trigger the growth of its imports from Korea? And what’s the impact of China’s final demands on the import in different industries? Design/methodology/approach Based on the Multi-Regional Input-Output model and World Input-Output Table database, this paper constructs the non-competitive imports input-output (IO) table of China to Korea. According to this table, we can calculate the induced imports coefficient and comprehensive induced import coefficients of China’s four final demands for imports from Korea in the 56 industries in China. Findings Among the four driving forces, the strongest one is changes in inventories and valuables. The impact of final consumption expenditure and fixed capital formation is much lower than that of changes in inventories and valuables, but they have a broader impact for the 56 industries. This paper finds out the China’s import induction of the final demands to Korea peaked in 2005 and 2010 and decreased greatly in 2014, so the position of China as market provider for Korea will no longer rise substantially, contrarily it will be in a steady state. Originality/value First, this paper constructs the non-competitive IO table to analyze the market provider issues between two countries and provides practical ways and methods for studies on the issues of imports and market provider. Second, this paper investigates the different roles of four final demands on driving force of China as market provider for Korea and the structural changes of China as a market provider for Korea among 56 industries from 2000 to 2014.

Study on the Steering Performance of Dual-Motor Drive Track Bulldozer

2013 ◽  
Vol 427-429 ◽  
pp. 133-136
Author(s):  
Qiang Song ◽  
Pu Zeng
Keyword(s):  
Simulation Model ◽  
Dynamic Characteristics ◽  
Driving Force ◽  
Driving Forces ◽  
Small Radius ◽  
Motor Drive ◽  
Matlab Simulink ◽  
Simulation Results ◽  
Two Sides

The driving theory and the dynamic characteristics of small radius steering, medium radius steering and big radius steering is analyzed, and the simulation model is established under Matlab/Simulink. Then the track bulldozers steering performance of the three sheerings is simulated. The results show that, at different steering modes, the running states of the two sides driving motors are not the same, and the track driving forces of the two sides vary widely. The track driving force is great in the small radius steering model, while small in the medium and big radius steering models. The simulation results lay the foundation for dual-motor drive track bulldozers steering performance matching.

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