Atomic-Scale Computer Simulation for early Precipitation Process of Ni75AlXV25-X Alloy with Middle Al Composition

2011 ◽  
Vol 704-705 ◽  
pp. 1328-1337
Author(s):  
Yu Hong Zhao ◽  
Hua Hou ◽  
Yu Hui Zhao
Keyword(s):  
Spinodal Decomposition ◽  
Volume Fraction ◽  
Transition Process ◽  
Nucleation And Growth ◽  
Atomic Scale ◽  
Precipitation Process ◽  
Atom Fraction ◽  
Precipitation Mechanism ◽  
Al Content ◽  
Ordered Phases

The microscopic phase field approach was applied for modeling the early precipitation process of Ni75AlxV25-xalloy. Without any a prior assumption, this model can be used to simulate the temporal evolution of arbitrary morphologies and microstructures on atomic scale. Through the simulated atomic pictures, calculated order parameters and volume fraction of the θ (Ni3V) and γ′ (Ni3Al) ordered phases, Ni75AlxV25-xalloys with Al composition of 0.05, 0.053 and 0.055 (atom fraction) were studied. Results show: For these alloys, θ and γ′ precipitated at the same time. With the increase of Al content, the amount of γ′ phase is increasing and that of θ phase is decreasing; the precipitation characteristic of γ′ phase transforms from Non-Classical Nucleation and Growth (NCNG) to Congruent Ordering + Spinodal Decomposition (CO+SD) gradually, otherwise, the precipitation characteristic of θ phase transforms from Congruent Ordering + Spinodal Decomposition (CO+SD) to Non-Classical Nucleation and Growth (NCNG) mechanism gradually. Both θ and γ′ has undergone the transition process of mixture precipitation mechanism with the characteristic of both NCNG and CO+SD mechanism. No incontinuous transition of precipitation mechanism has been found.

Atomic-Scale Computer Simulation of Mixture Precipitation Mechanism for Ni75AlxV25-x Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 3115-3118 ◽  
Author(s):  
Yu Hong Zhao ◽  
Dong Ying Ju ◽  
Hua Hou
Keyword(s):  
Computer Simulation ◽  
Spinodal Decomposition ◽  
Field Model ◽  
Phase Field Model ◽  
Nucleation And Growth ◽  
Atomic Scale ◽  
Precipitation Mechanism ◽  
Ordered Phases ◽  
Nucleation And Growth Mechanism ◽  
Microscopic Phase Field Model

With the microscopic phase-field model, the early precipitation mechanisms of the ternary Ni75AlxV25-x alloys with middle Al composition were explored by computer simulation in this paper. Through the simulated atomic pictures and composition order parameters of precipitates, we can explain the complex precipitation mechanisms of θ (Ni3V) and γ′ (Ni3Al) ordered phases. Simulated results also show that the precipitation characteristic of γ′ phase transforms from non-classical nucleation and growth to congruent ordering + Spinodal decomposition gradually, otherwise, the precipitation characteristic of θ phase transforms from congruent ordering + Spinodal decomposition to non-classical nucleation and growth mechanism gradually.

Computer Simulation of the Early Stage of Precipitation of L12-Ni3(Al,V) Using Microscopic Phase Field Method

2015 ◽  
Vol 817 ◽  
pp. 809-815
Author(s):  
Wei Ping Dong ◽  
Zheng Chen
Keyword(s):  
Spinodal Decomposition ◽  
Phase Field ◽  
Early Stage ◽  
Equilibrium Phase ◽  
Field Method ◽  
Phase Field Method ◽  
Precipitation Process ◽  
Interatomic Potentials ◽  
Precipitation Mechanism ◽  
Precipitation Phase

Based on the phase field theory, the long-range order (LRO) parameter related interatomic potentials equations were utilized to calculate the interatomic potentials of L10-Ni3(Al,V), L12-Ni3Al and L12-Ni3(Al,V) phases varying with temperature and concentrations. Using these potentials, the simulated microstructure evolution and the order parameter with the time of Ni75Al20V5 ternary alloy are simulated at temperature 1000K during the early stage of the precipitation process in this research. Results testify that the precipitation sequence during the early stage of Ni75Al20V5 alloy is the disordered phase →L10 pre-precipitation phase →L12 equilibrium phase. Firstly, the nonstoichiometric L10 pre-precipitation phase formed by congruent ordering precipitation mechanism; secondly, the nonstoichiometric L12 phase formed by transforming from L10 phase; thirdly, the stoichiometric equilibrium L12 phase formed by spinodal decomposition precipitation mechanism. It is discovered that the precipitation mechanism (congruent ordering+ spinodal decomposition) process was closely related to free energy and interatomic potentials: L10 pre-precipitation phase’s free energies are higher and interatomic potentials are smaller than those of L12 equilibrium phase.

Microscopic Phase-Field Simulation of the Process of Middle Heat Treatment of Ni-Cr-Al Alloy

2011 ◽  
Vol 80-81 ◽  
pp. 36-39
Author(s):  
Zhong Chu ◽  
Guo Qun Zhao
Keyword(s):  
Heat Treatment ◽  
Phase Field ◽  
Field Model ◽  
Volume Fraction ◽  
Phase Field Model ◽  
Nucleation And Growth ◽  
Al Alloy ◽  
Precipitation Mechanism ◽  
Microscopic Phase Field Model ◽  
Strengthening Phases

The effect of the middle heat treatment+aging(1323K+1073K) for the precipitation mechanism and volume fraction of Ni-11at.%Cr-17at.%Al ternary alloy are studied based on microscopic phase-field model. The results show that the precipitation mechanism is non-classical nucleation and growth for the alloy at middle heat treatment, and the congruent ordering and spinodal decomposition mechanism occur at single-stage aging. The larger precipitation strengthening phases are obtained, the volume fraction of ordering phases and the averaged ordering parameter are higher, and the incubation period prolongs after the middle heat treatment.

Direct imaging of order-disorder and antiphase domain structures in Ti3Al intermetallic compound

1990 ◽  
Vol 48 (4) ◽  
pp. 480-481
Author(s):  
H. Q. Ye ◽  
T.S. Xie ◽  
D. Li
Keyword(s):  
Intermetallic Compound ◽  
Volume Fraction ◽  
Fundamental Problem ◽  
Antiphase Domain ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Domain Structures ◽  
Α Phase ◽  
Diffraction Patterns ◽  
Two Phases

The Ti3Al intermetallic compound has long been recognized as potentially useful structural materials. It offers attractive strength to weight and elastic modulus to weight ratios. Recent work has established that the addition of Nb to Ti3Al ductilized this compound. In this work the fundamental problem of this alloy, i.e. order-disorder and antiphase domain structures was investigated at the atomic scale.The Ti3Al+10at%Nb alloys used in this study were treated at 1060°C and then aged at 700°C for 2 hours. The specimens suitable for TEM were prepared by standard jet electrolytic-polishing technique. A JEM-200CX electron microscope with an interpretable resolution of about 0.25 nm was used for HREM.The [100] and [001] projections of the α2 phase were shown in Fig.l.The alloy obtained consist of at least two phases-α2(Ti3Al) and β0 structures. Moreover, a disorder α phase with small volume fraction was also observed. Fig.2 gives [100] and [001] diffraction patterns of the α2 phase. Since lattice parameters of the ordered α2 (a=0.579, c=0.466 nm) and disorder α phase (a0=0.294≈a/2, c0=0.468 nm) are almost the same, their diffraction patterns are difficult to be distinguished when they are overlapped with epitaxial orientation relationships.

scholarly journals The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

2021 ◽  
Vol 11 (8) ◽  
pp. 3378
Author(s):  
Jie Chen ◽  
Darby J. Luscher ◽  
Saryu J. Fensin
Keyword(s):  
Growth Model ◽  
Damage Evolution ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Nucleation And Growth ◽  
Void Coalescence ◽  
Hydrodynamic Simulations ◽  
Void Evolution ◽  
Void Nucleation And Growth ◽  
Nucleation Growth

A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

In Situ Observation of Nucleation and Growth of Carbon Nanotubes from Iron Carbide Nanoparticles

2008 ◽  
Vol 1142 ◽  
Author(s):  
Hideto Yoshida ◽  
Seiji Takeda ◽  
Tetsuya Uchiyama ◽  
Hideo Kohno ◽  
Yoshikazu Homma
Keyword(s):  
Carbon Nanotubes ◽  
Iron Carbide ◽  
Bulk Diffusion ◽  
Chemical Vapor ◽  
Nucleation And Growth ◽  
Atomic Scale ◽  
In Situ Observation ◽  
Transmission Electron ◽  
Cvd Growth

ABSTRACTNucleation and growth processes of carbon nanotubes (CNTs) in iron catalyzed chemical vapor deposition (CVD) have been observed by means of in-situ environmental transmission electron microscopy. Our atomic scale observations demonstrate that solid state iron carbide (Fe3C) nanoparticles act as catalyst for the CVD growth of CNTs. Iron carbide nanoparticles are structurally fluctuated in CVD condition. Growth of CNTs can be simply explained by bulk diffusion of carbon atoms since nanoparticles are carbide.

Formabilities of C-Si-Al-Mn Transformation-Induced Plasticity-Aided Martensitic Sheet Steel

2016 ◽  
Vol 838-839 ◽  
pp. 546-551
Author(s):  
Junya Kobayashi ◽  
Yumenori Nakashima ◽  
Koh Ichi Sugimoto ◽  
Goroh Itoh
Keyword(s):  
Tensile Strength ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Sheet Steel ◽  
Void Formation ◽  
High Volume ◽  
Stress Concentrations ◽  
Transformation Induced Plasticity ◽  
Al Content

The substitution of Si with Al in 0.2%C-1.5%Si-1.25%Mn-0.2%Cr ultrahigh strength transformation-induced plasticity (TRIP)-aided martensitic (TM) sheet steel improves galvanization. The effect of Al content on the microstructure and formabilities of the TM steel was therefore investigated. Replacement of Si with Al maintained the high volume fraction of the retained austenite and the high stretch-formability and stretch-flangeability, whereas it decreased the tensile strength. Complex addition of Si and Al yielded the best formabilities with 1.5 GPa tensile strength grade. The superior formabilities of Si-Al bearing TM steel were attributed to the strain-induced transformation of the metastable retained austenite and the relatively soft lath-martensite structure matrix. The former leads to plastic relaxation of the localized stress concentrations, thus suppressing void formation.

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