Tuning the creep rates of binary Al alloys by considering the effects of the stacking faults, alloying elements, and elastic moduli: a first-principles study

2018 ◽  
Vol 96 (7) ◽  
pp. 755-759
Author(s):  
T. Todorova ◽  
J.W. Zwanziger
Keyword(s):  
Aluminum Alloys ◽  
Elastic Properties ◽  
First Principles ◽  
Elastic Moduli ◽  
Activation Barrier ◽  
Stacking Faults ◽  
Al Alloys ◽  
First Principles Calculations ◽  
Low Levels ◽  
Stacking Fault Energies

Using first-principles calculations, the effects of intrinsic stacking faults, elastic moduli, and diffusivity on the creep rates of aluminum alloys Al–X (X = Sc, Nb, or Mo) have been investigated. The calculated stacking fault energies of dilute Al show stabilization in the case of Sc and destabilization in the case of Mo and Nb. Although all three impurities confer stiffer elastic properties, Sc appears to retain the ductility of Al but Mo and Nb push the system in the brittle regime. Also, Mo and Nb strongly increase the activation barrier to diffusion, leading to much reduced creep. The results indicate that Mo and Nb can be used in Al alloys to improve elastic properties and creep resistance but only at very low levels, before brittleness becomes an issue.

Effect of Alloying Elements on the Elastic Properties of γ-Ni and γ'-Ni3Al from First-principles Calculations

2009 ◽  
Vol 1224 ◽  
Author(s):  
Yunjiang Wang ◽  
Chongyu Wang
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Elastic Moduli ◽  
Lattice Misfit ◽  
Alloying Elements ◽  
First Principles Calculations ◽  
Strengthening Mechanisms ◽  
Two Phases ◽  
Effect Of Alloying

AbstractThe effect of alloying elements Ta, Mo, W, Cr, Re, Ru, Co, and Ir on the elastic properties of both γ-Ni and γ′-Ni3Al is studied by first-principles method. Results for lattice properties, elastic moduli and the ductile/brittle behaviors are all presented. Our calculated values agree well with the existing experimental observations. Results show all the additions decrease the lattice misfit between and γ′ phases. Different alloying elements are found to have different effect on the elastic moduli of γ-Ni. Whereas all the alloying elements slightly increase the moduli of γ′-Ni3Al expect Co. Both of the two phases are becoming more brittle with alloying elements, but Co is excepted. The electronic structures of γ′ phase alloyed with different elements are provided as example to elucidate the different strengthening mechanisms.

First-Principles Calculations of the Mechanical and Elastic Properties of 2Hc- and 2Ha-WS2/CrS2 Under Pressure

2016 ◽  
Vol 71 (6) ◽  
pp. 517-524 ◽  
Author(s):  
Hua-Long Jiang ◽  
Song-Hao Jia ◽  
Da-Wei Zhou ◽  
Chun-Ying Pu ◽  
Fei-Wu Zhang ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Elastic Properties ◽  
First Principles ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
First Principles Calculations ◽  
Stability Criteria ◽  
Poisson Coefficient ◽  
Debye Temperatures ◽  
Two Phases

AbstractBy utilizing the first-principles method, the pressure-induced effects on phase transition, mechanical stability, and elastic properties of WS2/CrS2 are investigated in the pressure range from 0 to 80 GPa. Transitions from 2Hc to 2Ha for WS2 and CrS2 are found to occur at 17.5 and 25 GPa, respectively. It is found that both 2Ha and 2Hc phases of WS2 and CrS2 meet the mechanical stability criteria up to 80 GPa, suggesting that those structures are mechanically stable. The bulk and shear modulus anisotropy of the two phases of WS2 and CrS2 decrease rapidly under pressure and, finally, trend to isotropy. With increasing pressure, the elastic moduli (Y, B, and G), sound velocities (vs, vp, vm), and Debye temperatures (Θ) of 2Ha and 2Hc of WS2 and CrS2 increase monotonously. Moreover, the Debye temperature (Θ) of 2Hc phase is higher than that of 2Ha phase for both WS2 and CrS2. The bulk, shear, and Young’s modulus, Poisson coefficient, and brittle/ductile behaviour are estimated. The percentages of anisotropy in compressibility and shear and the ratio of bulk to shear modulus (B/G) are also studied.

scholarly journals Elastic Properties and Stacking Fault Energies of Borides, Carbides and Nitrides from First-Principles Calculations

2019 ◽  
Vol 32 (9) ◽  
pp. 1099-1110 ◽  
Author(s):  
Yong Zhang ◽  
Zi-Ran Liu ◽  
Ding-Wang Yuan ◽  
Qin Shao ◽  
Jiang-Hua Chen ◽  
...  
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Stacking Fault ◽  
First Principles Calculations ◽  
Stacking Fault Energies

scholarly journals Effects of alloying elements on elastic properties of Al by first-principles calculations

2014 ◽  
Vol 50 (1) ◽  
pp. 37-44 ◽  
Author(s):  
J. Wang ◽  
Y. Du ◽  
S.L. Shang ◽  
Z.K. Liu ◽  
Y. Li
Keyword(s):  
Bulk Modulus ◽  
Elastic Properties ◽  
First Principles ◽  
Al Alloys ◽  
Alloying Elements ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Polycrystalline Aggregates ◽  
Relationship Of ◽  
G Ratio

The effects of alloying elements (Co, Cu, Fe, Ge, Hf, Mg, Mn, Ni, Si, Sr, Ti, V, Y, Zn, and Zr) on elastic properties of Al have been investigated using first-principles calculations within the generalized gradient approximation. A supercell consisting of 31 Al atoms and one solute atom is used. A good agreement is obtained between calculated and available experimental data. Lattice parameters of the studied Al alloys are found to be depended on atomic radii of solute atoms. The elastic properties of polycrystalline aggregates including bulk modulus (B), shear modulus (G), Young?s modulus (E), and the B/G ratio are also determined based on the calculated elastic constants (cij?s). It is found that the bulk modulus of Al alloys decreases with increasing volume due to the addition of alloying elements and the bulk modulus is also related to the total molar volume (Vm) and electron density (nAl31x) with the relationship of nAl31x=1.0594+0.0207?B/Vm. These results are of relevance to tailor the properties of Al alloys.

scholarly journals First Principles Investigation on Thermodynamic Properties and Stacking Fault Energy of Paramagnetic Nickel at High Temperatures

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 319
Author(s):  
Jing Zhang ◽  
Pavel A. Korzhavyi
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Temperature Dependence ◽  
First Principles ◽  
Elastic Moduli ◽  
Stacking Faults ◽  
Lattice Parameter ◽  
Stacking Fault ◽  
Stacking Fault Energies

Reliable data on the temperature dependence of thermodynamic properties of alloy phases are very useful for modeling the behavior of high-temperature materials such as nickel-based superalloys. Moreover, for predicting the mechanical properties of such alloys, additional information on the energy of lattice defects (e.g., stacking faults) at high temperatures is highly desirable, but difficult to obtain experimentally. In this study, we use first-principles calculations, in conjunction with a quasi-harmonic Debye model, to evaluate the Helmholtz free energy of paramagnetic nickel as a function of temperature and volume, taking into account the electronic, magnetic, and vibrational contributions. The thermodynamic properties of Ni, such as the equilibrium lattice parameter and elastic moduli, are derived from the free energy in the temperature range from 800 to 1600 K and compared with available experimental data. The derived temperature dependence of the lattice parameter is then used for calculating the energies of intrinsic and extrinsic stacking faults in paramagnetic Ni. The stacking fault energies have been evaluated according to three different methodologies, the axial-next-nearest-neighbor Ising (ANNNI) model, the tilted supercell approach, and the slab supercell approach. The results show that the elastic moduli and stacking fault energies of Ni decrease with increasing temperature. This “softening” effect of temperature on the mechanical properties of nickel is mainly due to thermal expansion, and partly due to magnetic free energy contribution.

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