scholarly journals Influence of Cr, Mn, Co and Ni Addition on Crystallization Behavior of Al13Fe4 Phase in Al-5Fe Alloys Based on ThermoDynamic Calculations

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 768
Author(s):  
Na Pang ◽  
Zhiming Shi ◽  
Cunquan Wang ◽  
Ninyu Li ◽  
Yaming Lin
Keyword(s):  
Free Energy ◽  
Grain Refinement ◽  
Gibbs Free Energy ◽  
Formation Enthalpy ◽  
Wilson Equation ◽  
Obvious Effect ◽  
Ni Addition ◽  
Coarse Grains ◽  
Refinement Mechanism ◽  
Fe Alloys

Alloying is an effective method to refine coarse grains of an Al13Fe4 phase and strengthen Al-Fe alloys. However, the grain refinement mechanism remains unclear in terms of the thermodynamics. Herein, the influence of M-element, i.e., Cr, Mn, Co and Ni, addition on the activity of Al and Fe atoms, Gibbs free energy of the Al13Fe4 nucleus in Al-Fe melt and the formation enthalpy of an Al13Fe4 phase in Al-Fe alloys is systematically investigated using the extended Miedema model, Wilson equation, and first-principle calculations, respectively. The results reveal that the addition of different M elements increases the activity of Fe atoms and reduces the Gibbs free energy of the Al13Fe4 nucleus in Al-Fe melt, where the incorporation of Ni renders the most obvious effect, followed by Mn, Co, and Cr. Additionally, the formation enthalpy decreases in the following order: Al78(Fe23Cr) > Al78(Fe23Mn) > Al13Fe4 > Al78(Fe23Ni) > Al78(Fe23Co), where the formation enthalpy of Al78(Fe23Ni) is close to Al78(Fe23Co). Moreover, the presence of Ni promotes the nucleation of the Al13Fe4 phase in Al-Fe alloys, which reveals the mechanism of grain refinement from a thermodynamics viewpoint.

Effect of Electromagnetic Field on the Solidification Structure of Copper-Iron Alloys

2011 ◽  
Vol 217-218 ◽  
pp. 1492-1496
Author(s):  
Bao Mian Li ◽  
Hai Tao Zhang ◽  
Jian Zhong Cui
Keyword(s):  
Grain Size ◽  
Electromagnetic Field ◽  
Grain Refinement ◽  
Iron Content ◽  
Iron Alloys ◽  
Solidification Structure ◽  
Obvious Effect ◽  
The Matrix ◽  
Petal Shape ◽  
Fe Alloys

The effect of electromagnetic field and iron content on the solidification structure of copper-iron alloys had been investigated in this paper. The results show that the addition of iron to copper causes considerable grain refinement, and the refinement increases with the iron content. Applying electromagnetic field during the solidification of Cu-Fe alloys can further refine grain of hepoperitectic alloys, but has no obvious effect on the grain size of heperperitectic alloys. Primary γ-Fe dendrites are gradually broken and scattered uniformly throughout the matrix under the influence of electromagnetic field. When the current intensity is 200A, the primary γ-Fe appears as fine petal shape distributed uniformly over the matrix.

Quantum confinement effects of formation energies and vibrational properties of CdS clusters: A DFT study

2019 ◽  
Vol 33 (16) ◽  
pp. 1950163 ◽  
Author(s):  
Bahjat B. Kadhim ◽  
Mudar Ahmed Abdulsattar ◽  
Ali Mohammed Ali
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Rock Salt ◽  
Density Functional ◽  
Energy Gap ◽  
Formation Enthalpy ◽  
Longitudinal Optical ◽  
Enthalpy And Entropy ◽  
The Difference ◽  
Formation Energies

Formation energies of cadmium sulfide clusters are calculated with the help of density functional theory. The investigated structures include clusters that represent the CdS three main phases, wurtzite, zincblende and rock-salt. The investigation includes electronic, vibrational and thermal properties. CdS clusters are represented by wurtzoids, diamondoids and cuboids for the three phases, wurtzite, zincblende and rock-salt, respectively. The energy gap of the largest investigated molecules approaches that of bulk experimental 2.42 eV. The calculated longitudinal optical (LO) vibrational mode is 304.2 cm[Formula: see text] which is in good agreement with the experimental bulk value of 305 cm[Formula: see text]. To calculate Gibbs free energy, enthalpy and entropy of formation for the clusters, we redefined these quantities so that they represent the difference between the CdS formation energy and their constitutes Cd and S clusters energy. The calculated Gibbs free energy of formation, enthalpy and entropy of the investigated clusters approach that of bulk. Wurtzoids are more stable than diamondoids and cuboids with the release of more heat as deduced from their cluster Gibbs energy and enthalpy of formation. The entropy of clusters is dependent on the size of the cluster. The present method draws a relation between known solid state phases and small cluster calculations.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

Extended Gibbs Free Energy and Laplace Pressure of Ordered Hexagonal Close-Packed Spherical Particles: A Wettability Study

Langmuir ◽  
2021 ◽  
Author(s):  
Amir Bayat ◽  
Mahdi Ebrahimi ◽  
Saeed Rahemi Ardekani ◽  
Esmaiel Saievar Iranizad ◽  
Alireza Zaker Moshfegh
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Laplace Pressure ◽  
Spherical Particles ◽  
Hexagonal Close Packed

scholarly journals First-Principles Study of Mechanical and Thermodynamic Properties of Binary and Ternary CoX (X = W and Mo) Intermetallic Compounds

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1404
Author(s):  
Yunfei Yang ◽  
Changhao Wang ◽  
Junhao Sun ◽  
Shilei Li ◽  
Wei Liu ◽  
...  
Keyword(s):  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Vibrational Entropy ◽  
Functional Theory ◽  
Lattice Constants ◽  
The Density Functional Theory ◽  
Ductile Behavior ◽  
Pseudo Potential

In this study, the structural, elastic, and thermodynamic properties of DO19 and L12 structured Co3X (X = W, Mo or both W and Mo) and μ structured Co7X6 were investigated using the density functional theory implemented in the pseudo-potential plane wave. The obtained lattice constants were observed to be in good agreement with the available experimental data. With respect to the calculated mechanical properties and Poisson’s ratio, the DO19-Co3X, L12-Co3X, and μ-Co7X6 compounds were noted to be mechanically stable and possessed an optimal ductile behavior; however, L12-Co3X exhibited higher strength and brittleness than DO19-Co3X. Moreover, the quasi-harmonic Debye–Grüneisen approach was confirmed to be valid in describing the temperature-dependent thermodynamic properties of the Co3X and Co7X6 compounds, including heat capacity, vibrational entropy, and Gibbs free energy. Based on the calculated Gibbs free energy of DO19-Co3X and L12-Co7X6, the phase transformation temperatures for DO19-Co3X to L12-Co7X6 were determined and obtained values were noted to match well with the experiment results.

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