scholarly journals Structural Properties and Phase Stability of Primary Y Phase (Ti2SC) in Ti-Stabilized Stainless Steel from Experiments and First Principles

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1118 ◽  
Author(s):  
Deli Zhao ◽  
Yu Zhou ◽  
Jiangyu Fan ◽  
Tianyu Liu ◽  
Yihong Nie ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Phase Stability ◽  
First Principles ◽  
Mechanical Stability ◽  
Hexagonal Structure ◽  
Covalent Interaction ◽  
Microstructural Evaluation ◽  
Brittle Phase ◽  
Two Phases ◽  
Aisi 321

The morphology and microstructural evaluation of Y phases in AISI 321 (a Ti-stabilized stainless steel) were characterized after hot deformation. The electronic structure and phase stability of titanium carbosulfide were further discussed by first-principle calculations. It was found that Y phases, like curved strips or bones in AISI 321 stainless steel, mostly show a clustered distribution and are approximately arranged in parallel. The width of the Y phase is much less than the length, and the composition of the Y phase is close to that of Ti2SC. Y phases have exceptional thermal stability. The morphology of Y phases changed considerably after forging. During the first calculations, the Ti2SC with hexagonal structure does not spontaneously change into TiS and TiC; however Ti4S2C2 (Z = 2) can spontaneously change into the two phases. The Ti–S bonds are compressed in Ti4S2C2 cells, which leads to poor structural stability for Ti4S2C2. There is a covalent interaction between C/S and Ti, as well as an exchange of electrons between Ti and S/C atoms. Evidently, the mechanical stability of Ti4S2C2 is weak; however, Ti2SC shows high stability. Ti2SC, as a hard brittle phase, does not easily undergo plastic deformation.

First principles study of ground-state properties of Laves phase ZrMn2 and its hydride

2018 ◽  
Vol 84 (1) ◽  
pp. 10901
Author(s):  
Zhi-Sheng Nong ◽  
Yu-Nong Lei ◽  
Jing-Chuan Zhu
Keyword(s):  
Ground State ◽  
First Principles ◽  
Mechanical Stability ◽  
Laves Phase ◽  
Elastic Behavior ◽  
Calculated Density ◽  
Covalent Interaction ◽  
Density Distributions ◽  
Formation Enthalpies ◽  
Storage Behavior

The structural stability, elastic properties and bonding behavior of Laves phase ZrMn2 with C14, C15 and C36 structures as well as its hydride ZrMn2-H3 considering ferromagnetic (FM) ordering state were investigated by the first principles calculations. The calculated formation enthalpies and mechanical stability confirmed C14 structure is the stable crystal for ZrMn2 in FM ground state. A better hydrogen storage behavior of C14 phase ZrMn2 was predicted due to the obtained lower binding energy of hydrogen in ZrMn2-H3. In addition, there would be transformation of elastic behavior from ductility to brittleness, and increasing isotropy for ZrMn2 when H atoms are absorbed into 12k sites of crystal structure to form hydride ZrMn2-H3. The calculated density of states, charge density distributions and Mulliken populations revealed that additional hybridizations and covalent interaction between Zr and H atoms would be introduced with the absorption of H atoms in C14-phase ZrMn2.

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.

Structures, elastic, electronic properties and phase stability of Ni–Sc intermetallic compounds from first-principles investigation

2018 ◽  
Vol 32 (24) ◽  
pp. 1850262 ◽  
Author(s):  
Yali Wu ◽  
Xuefeng Guo
Keyword(s):  
Shear Modulus ◽  
Electronic Properties ◽  
Intermetallic Compounds ◽  
Phase Stability ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Ductile Phase ◽  
Covalent Bonds ◽  
Debye Temperatures

First-principles method based on density functional theory has been performed to study the lattice structures, elastic properties, Debye temperatures, electronic properties and phase stability of Ni–Sc intermetallic compounds systematically. The calculated lattice parameters are close to available experimental data. The analysis results of formation enthalpies indicate that the Ni–Sc compounds are all thermodynamically stable and NiSc is the most stable. Besides, these compounds are also mechanically stable according to the mechanical stability criterion. The obtained shear modulus G and Young’s modulus E show that Ni5Sc is the stiffest and the most covalent compound. The discussion about G/B (the ratio of shear modulus to bulk modulous), Poisson’s ratio [Formula: see text] and Cauchy pressure demonstrate that all Ni–Sc compounds are ductile and NiSc2 is the most ductile phase, followed by NiSc. The results of Debye temperatures indicate that Ni5Sc has the stronger covalent bonds than others. Finally, the electronic properties are investigated to reveal the underlying mechanical properties.

scholarly journals Novel structural phases and the properties of LaX (X = P, As) under high pressure: first-principles study

RSC Advances ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 3058-3070
Author(s):  
Yu Zhou ◽  
Lan-Ting Shi ◽  
A-Kun Liang ◽  
Zhao-Yi Zeng ◽  
Xiang-Rong Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Pressure Range ◽  
Mechanical Stability ◽  
First Principles Study

The structures, phase transition, mechanical stability, electronic structures, and thermodynamic properties of lanthanide phosphates (LaP and LaAs) are studied in the pressure range of 0 to 100 GPa by first principles.

The corrosion inhibition of stainless steel by ferrocene–polyoxometalate hybrid molecular materials – experimental and first principles studies

2020 ◽  
Vol 22 (6) ◽  
pp. 3329-3344 ◽  
Author(s):  
G. Sruthi ◽  
K. Shakeela ◽  
R. Shanmugam ◽  
G. Ranga Rao
Keyword(s):  
Stainless Steel ◽  
Corrosion Inhibition ◽  
Hybrid Material ◽  
First Principles ◽  
Inhibition Mechanism ◽  
Molecular Materials

The corrosion inhibition mechanism for SS316 coated with FcPMo hybrid material is shown.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

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