Prediction of the kink-pair formation enthalpy on screw dislocations inα-iron by a line tension model parametrized on empirical potentials and first-principles calculations

2013 ◽  
Vol 87 (14) ◽  
Author(s):  
Laurent Proville ◽  
Lisa Ventelon ◽  
David Rodney
Keyword(s):  
First Principles ◽  
Formation Enthalpy ◽  
Line Tension ◽  
Pair Formation ◽  
First Principles Calculations ◽  
Screw Dislocations ◽  
Kink Pair ◽  
Empirical Potentials

Effect of Cr doping on the mechanical properties and electronic structure of WCoB ternary boride by first-principles calculations

2018 ◽  
Vol 32 (21) ◽  
pp. 1850240 ◽  
Author(s):  
Tong Zhang ◽  
Haiqing Yin ◽  
Cong Zhang ◽  
Xuanhui Qu ◽  
Qingjun Zheng
Keyword(s):  
Mechanical Properties ◽  
Electronic Structure ◽  
Structural Stability ◽  
First Principles ◽  
Formation Enthalpy ◽  
First Principles Calculations ◽  
Metal Interactions ◽  
Metal Metal ◽  
Ternary Boride ◽  
Cr Doping

The lattice parameters, structural stability, mechanical properties, hardness and electronic structure of WCoB with Cr alloying were investigated by using first-principles calculations. The Cr atom was selected to replace 0, 1, 2, 3, 4 Co atoms in WCoB crystal and 0, 1, 2 Co atoms in W2CoB2 crystal. The calculated cohesive energy and formation enthalpy showed that all structures can retain good structural stability with different Cr doping content. The calculated mechanical properties showed Cr doping will decrease the shear modulus, Young’s modulus, bulk modulus and hardness, but increase the ductility. The larger number of valence electrons of Cr led to the increasing of bond covalence and population. According to the electronic structures analysis, the nonmetal–metal hybridization and metal–metal interactions contributed to relatively high toughness.

The Effect of Cr Addition on the Microstructure of TiNi: First-Principles Calculations

2014 ◽  
Vol 881-883 ◽  
pp. 1351-1354
Author(s):  
Wei Bing Zhang ◽  
Kai Long ◽  
Xiao Cheng
Keyword(s):  
Binding Energy ◽  
Plane Wave ◽  
First Principles ◽  
Niti Alloy ◽  
Formation Enthalpy ◽  
Wave Method ◽  
First Principles Calculations ◽  
Plane Wave Method ◽  
Cr Addition ◽  
Pseudo Potential

Based on the first-principles pseudo-potential plane wave method, the effect of Cr addition on the microstructure of NiTi alloys are characterized and assessed with the formation enthalpy (ΔH), binding energy (ΔE) and density of states (DOS) distribution of NiTi (Cr) crystals. The results show that the binding energy of NiTi (CrNi) is slightly smaller than that of NiTi (CrTi), but the formation enthalpy of NiTi (CrTi) is much smaller than that of NiTi (CrNi).So the Ms of NiTi alloy could be decreased by the addition of ratio for Ni/Ti. And the electronic microstucture of NiTi (CrNi) alloy are also illustrated clearly.

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.

The structural stabilities, mechanical properties and hardness of chromium tetraboride: Compared with low-B borides

2016 ◽  
Vol 30 (30) ◽  
pp. 1650201 ◽  
Author(s):  
Ming-Min Zhong ◽  
Cheng Huang ◽  
Chun-Ling Tian
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Boron Content ◽  
Three Dimensional ◽  
Formation Enthalpy ◽  
Structural Features ◽  
Relative Energy ◽  
First Principles Calculations ◽  
Systemic Understanding ◽  
Opposite Tendency

Using the first-principles calculations, we provide a systemic understanding of the structural features and phase stability, mechanical and electronic properties, as well as the roles of boron (B) atom arrangement in the hardness for chromium borides. The structural and relative energy searches together with formation enthalpy confirm the most stable Cr2B with an orthorhombic Fddd symmetry, CrB with an orthorhombic Cmcm symmetry, CrB2 with a hexagonal P63/mmc symmetry and chromium tetraboride (CrB4) with an orthorhombic Pnnm symmetry. The shear modulus, Young’s modulus and [Formula: see text] increase with the boron content, while the Poisson’s ratio and [Formula: see text] ratio have an opposite tendency. Moreover, due to higher B content, strong three-dimensional (3D) covalent B networks and lower metallic contribution, CrB4 with Pnnm symmetry has the largest hardness value (46.8 GPa), exceeding the superhard limit, indicating its superhard nature.

Origin of dramatic oxygen solute strengthening effect in titanium

Science ◽  
2015 ◽  
Vol 347 (6222) ◽  
pp. 635-639 ◽  
Author(s):  
Qian Yu ◽  
Liang Qi ◽  
Tomohito Tsuru ◽  
Rachel Traylor ◽  
David Rugg ◽  
...  
Keyword(s):  
First Principles ◽  
Dislocation Core ◽  
Strengthening Effect ◽  
First Principles Calculations ◽  
Screw Dislocations ◽  
Elastic Fields ◽  
Transmission Electron ◽  
Short Range Repulsion ◽  
Solute Atoms ◽  
Solute Strengthening

Structural alloys are often strengthened through the addition of solute atoms. However, given that solute atoms interact weakly with the elastic fields of screw dislocations, it has long been accepted that solution hardening is only marginally effective in materials with mobile screw dislocations. By using transmission electron microscopy and nanomechanical characterization, we report that the intense hardening effect of dilute oxygen solutes in pure α-Ti is due to the interaction between oxygen and the core of screw dislocations that mainly glide on prismatic planes. First-principles calculations reveal that distortion of the interstitial sites at the screw dislocation core creates a very strong but short-range repulsion for oxygen that is consistent with experimental observations. These results establish a highly effective mechanism for strengthening by interstitial solutes.

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