Characterizing Deformation Mechanisms in Ni3Ge-Fe3Ge Intermetallic Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
T. J. Balk ◽  
Mukul Kumar ◽  
O. N. Mryasov ◽  
A. J. Freeman ◽  
K. J. Hemker
Keyword(s):  
Yield Strength ◽  
First Principles ◽  
Elastic Moduli ◽  
Intermetallic Alloys ◽  
First Principles Calculations ◽  
Anomalous Temperature ◽  
Weak Beam ◽  
Planar Fault ◽  
Fe Content ◽  
Mechanisms Of Deformation

ABSTRACTThe Ni3Ge-Fe3Ge model system provides us with a unique opportunity to characterize the mechanisms of deformation in both anomalous and normal L12 intermetallic alloys. The elastic moduli of alloys in this system have been measured and used as benchmarks for first principles calculations. At 77K, increasing the Fe content has been found to result in a dramatic increase in flow stress. The Ni-rich alloys exhibit a yield strength anomaly, but as Ni is replaced by Fe, the anomalous temperature dependence gradually disappears, and no yield strength anomaly is observed for alloys with more than 25 at% Fe. At low temperatures and Fe contents, the deformation microstructure has been found to be dominated by Kear-Wilsdorf locking; but a transition from octahedral glide and Kear-Wilsdorf locking to cube glide is observed as either Fe content or temperature is increased. This transition is related to changes that occur in the core structures of dissociated superdislocations and planar fault energies measured through computer simulations of weak-beam TEM images.

scholarly journals Temperature Effects on the Elastic Constants, Stacking Fault Energy and Twinnability of Ni3Si and Ni3Ge: A First-Principles Study

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 364 ◽  
Author(s):  
Lili Liu ◽  
Liwan Chen ◽  
Youchang Jiang ◽  
Chenglin He ◽  
Gang Xu ◽  
...  
Keyword(s):  
Elastic Constants ◽  
First Principles ◽  
Antiphase Boundary ◽  
Stacking Fault ◽  
First Principles Calculations ◽  
Planar Fault ◽  
Different Temperatures ◽  
Generalized Stacking Fault ◽  
Increasing Temperature ◽  
Stacking Fault Energies

The volume versus temperature relations for Ni 3 Si and Ni 3 Ge are obtained by using the first principles calculations combined with the quasiharmonic approach. Based on the equilibrium volumes at temperature T, the temperature dependence of the elastic constants, generalized stacking fault energies and generalized planar fault energies of Ni 3 Si and Ni 3 Ge are investigated by first principles calculations. The elastic constants, antiphase boundary energies, complex stacking fault energies, superlattice intrinsic stacking fault energies and twinning energy decrease with increasing temperature. The twinnability of Ni 3 Si and Ni 3 Ge are examined using the twinnability criteria. It is found that their twinnability decrease with increasing temperature. Furthermore, Ni 3 Si has better twinnability than Ni 3 Ge at different temperatures.

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.

Relating Mechanical Properties with Dislocation Cores in Ni3Ge-Fe3Ge Intermetallic Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
T. John Balk ◽  
Mukul Kumar ◽  
Kevin J. Hemker
Keyword(s):  
Yield Stress ◽  
Mechanical Testing ◽  
Composition Range ◽  
Negative Temperature ◽  
Anomalous Behavior ◽  
Intermetallic Alloys ◽  
Complete Solid Solubility ◽  
Deformation Structures ◽  
Planar Fault ◽  
Fe Content

ABSTRACTThe transition from positive to negative temperature dependence of 0.2% yield stress is investigated m the model pseudo-binary Ni3Ge-Fe3Ge system. Ni3Ge and Fe3Ge, both Ll2 intermetallic alloys, show complete solid solubility as Fe is continuously substituted for Ni across the composition range. However, Ni3Ge exhibits the yield stress anomaly, whereas the yield stress of Fe3Ge shows a normal decline with temperature. Mechanical testing has verified this behavior, with the anomalous behavior gradually disappearing with increasing Fe content. It is proposed that this transition results from changes in the structure of dissociated superdislocation cores. Alloys with anomalous behavior from this system are characterized by the presence of screw superdislocations locked in the Kear-Wilsdorf (KW) configuration. Conversely, alloys with normal yield stress dependence are observed to contain curvilinear superdislocations that glide on the cube planes. Results from mechanical testing are presented and correlated with TEM observations of deformation structures. These results are discussed in light of planar fault energies determined through computer simulations of images.

First-Principles Investigation of Structural Stability, Mechanical, Anisotropic, and Thermodynamic Properties of CeT2Al20 Intermetallics

2018 ◽  
Vol 73 (12) ◽  
pp. 1157-1167 ◽  
Author(s):  
He Ma ◽  
Xiaoyou Li ◽  
Wei Jiang ◽  
Xudong Zhang
Keyword(s):  
High Temperature ◽  
Thermodynamic Properties ◽  
Thermodynamic Parameters ◽  
Structural Stability ◽  
Elastic Constants ◽  
First Principles ◽  
Elastic Moduli ◽  
Formation Enthalpy ◽  
First Principles Calculations ◽  
Acoustic Velocities

AbstractFirst-principles calculations were carried out to explore the structural stability, elastic moduli, ductile or brittle behaviour, anisotropy, dynamical stability, and thermodynamic properties of pure Al and CeT2Al20 (T = Ti, V, Cr, Nb, and Ta) intermetallics. The calculated formation enthalpy and phonon frequencies confirm that these intermetallics satisfy the conditions for structural stability. The elastic constants Cij, elastic moduli B, G, and E, and the hardness Hv indicate these intermetallics have higher hardness and the better resistance against deformation than pure Al. The values of Poisson’s ratio (v) and B/G indicate that CeT2Al20 intermetallics are all brittle materials. The anisotropic constants and acoustic velocities confirm that CeT2Al20 intermetallics are all anisotropic, but CeV2Al20, CeNb2Al20, and CeTa2Al20 are nearly isotropic. Importantly, the calculated thermodynamic parameters show that CeT2Al20 intermetallics exhibit better thermodynamic properties than pure Al at high temperature.

scholarly journals Phase Stability, Elastic Modulus and Elastic Anisotropy of X Doped (X = Zn, Zr and Ag) Al3Li: Insight from First-Principles Calculations

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 7
Author(s):  
Jinzhong Tian ◽  
Yuhong Zhao ◽  
Shengjie Ma ◽  
Hua Hou
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
First Principles Calculations ◽  
Stability Criteria ◽  
Longitudinal Sound Velocity ◽  
Positive Effect ◽  
Shear Planes

In present work, the effects of alloying elements X (X = Zn, Zr and Ag) doping on the phase stability, elastic properties, anisotropy and Debye temperature of Al3Li were studied by the first-principles method. Results showed that pure and doped Al3Li can exist and be stable at 0 K. Zn and Ag elements preferentially occupy the Al sites and Zr elements tend to occupy the Li sites. All the Cij obey the mechanical stability criteria, indicating the mechanical stability of these compounds. The overall anisotropy decreases in the following order: Al23Li8Ag > Al3Li > Al23Li8Zn > Al24Li7Zr, which shows that the addition of Zn and Zr has a positive effect on reducing the anisotropy of Al3Li. The shear anisotropic factors for Zn and Zr doped Al3Li are very close to one, meaning that elastic moduli do not strongly depend on different shear planes. For pure and doped Al3Li phase, the transverse sound velocities νt1 and νt2 among the three directions are smaller than the longitudinal sound velocity νl. Moreover, only the addition of Zn is beneficial to increasing the ΘD of Al3Li among the three elements.

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.

High elastic moduli, controllable bandgap and extraordinary carrier mobility in single-layer diamond

2020 ◽  
Vol 8 (39) ◽  
pp. 13819-13826
Author(s):  
Ting Cheng ◽  
Zhongfan Liu ◽  
Zhirong Liu
Keyword(s):  
Mechanical Strength ◽  
Electronic Properties ◽  
First Principles ◽  
Carrier Mobility ◽  
Room Temperature ◽  
Elastic Moduli ◽  
Single Layer ◽  
First Principles Calculations ◽  
High Mechanical Strength ◽  
Direct Bandgap

Fluorinated single layer diamond is found by first-principles calculations to be a wide-direct bandgap material at the Γ-point, exhibiting a high mechanical strength, adjustable electronic properties and extraordinary carrier mobility at room temperature.

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