scholarly journals Examining oxidation in β-NiAl and β-NiAl+Hf alloys by stochastic cellular automata simulations

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Indranil Roy ◽  
Pratik K. Ray ◽  
Ganesh Balasubramanian
Keyword(s):  
Cellular Automata ◽  
Grain Boundaries ◽  
Oxide Scale ◽  
Oxidation Kinetics ◽  
Basic Principles ◽  
Stochastic Cellular Automata ◽  
Scale Thickness ◽  
Alloy Oxidation ◽  
Ca Model ◽  
Kinetics Of

AbstractWe present results from a stochastic cellular automata (CA) model developed and employed for examining the oxidation kinetics of NiAl and NiAl+Hf alloys. The rules of the CA model are grounded in diffusion probabilities and basic principles of alloy oxidation. Using this approach, we can model the oxide scale thickness and morphology, specific mass change and oxidation kinetics as well as an approximate estimate of the stress and strains in the oxide scale. Furthermore, we also incorporate Hf in the grain boundaries and observe the “reactive element effect”, where doping with Hf results in a drastic reduction in the oxidation kinetics concomitant with the formation of thin, planar oxide scales. Interestingly, although we find that grain boundaries result in rapid oxidation of the undoped NiAl, they result in a slower-growing oxide and a planar oxide/metal interface when doped with Hf.

Morphology of Oxide Scale and Oxidation Kinetics of Low Carbon Steel

2014 ◽  
Vol 21 (3) ◽  
pp. 335-341 ◽  
Author(s):  
Guang-ming Cao ◽  
Xiao-jiang Liu ◽  
Bin Sun ◽  
Zhen-yu Liu
Keyword(s):  
Carbon Steel ◽  
Oxide Scale ◽  
Oxidation Kinetics ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Kinetics Of

Effects of Si Content on the Oxidation Behavior of Fe–Si Alloys in Air

2011 ◽  
Vol 696 ◽  
pp. 126-131 ◽  
Author(s):  
Takumi Nishimoto ◽  
Kazuhiko Honda ◽  
Yasumitsu Kondo ◽  
Kenichi Uemura
Keyword(s):  
Oxide Scale ◽  
Cross Sections ◽  
Oxidation Kinetics ◽  
Oxidation Behavior ◽  
Elemental Distribution ◽  
Oxide Scales ◽  
Scale Thickness ◽  
Internal Oxidation Zone ◽  
Diffusion Controlled ◽  
Si Content

The oxidation behavior of Fe–Si alloys at 1073K in air was investigated. The oxidation kinetics described by the parabolic rate law of diffusion controlled oxidation and the oxidation rate decrease with the increasing Si content. Fe-Si alloys were oxidized for different times at 1073K to obtain the same scale thickness of approximately 30μm. Observations of scale cross-sections indicated the structure of oxide scale and elemental distribution in oxide scales strongly depends on Si content. The oxide scale on Fe-Si alloys with low Si content consisted of three layers with an outer Fe2O3, an intermediate Fe3O4 and an inner FeO and some voids were formed in Fe3O4 and FeO layers. The Si-rich oxide layer was formed at the scale/alloy interface of Fe-Si alloys with high Si content. Furthermore, the amount of internal oxidation zone increased with the increasing Si content. Observations of scale cross-sections indicated that the structure of oxide scale and elemental distribution in oxide scale strongly depend on Si content.

Interfacial Solute-Atom Segregation: An Atomic-scale Ahenomenon with Implications for the Oxidation Kinetics of Pt-Al Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 770-771
Author(s):  
E.C. Dickey ◽  
K.B. Alexander ◽  
B.A. Pint
Keyword(s):  
Phase Transformations ◽  
Oxide Scale ◽  
Oxidation Kinetics ◽  
Solute Atom ◽  
Analytical Electron Microscopy ◽  
Atomic Scale ◽  
Scale Spallation ◽  
Oxidation Rates ◽  
Physical Phenomena ◽  
Kinetics Of

Interfacial solute-atom segregation is known to have profound effects on macroscopic physical properties (e.g. electronic transport or fracture toughness) in interface-influenced or controlled materials. It has recently been shown that solute-atom segregation also can play an influential role in the dynamics of phase transformations, in particular the oxidation kinetics of alumina-forming alloys such as PtAl. By coupling analytical electron microscopy (AEM) with conventional macroscopic oxidation studies, we have demonstrated that oxidation kinetics are affected by atomic-scale segregation of dopant species to the grain boundaries and metal-oxide boundaries in the system. Furthermore, these studies illustrate the utility of AEM techniques in elucidating the atomic-scale aspects of macroscopic physical phenomena such as phase transformations.Oxidation studies were carried out on PtAl alloys with and without small additions of Zr to the alloy. While the pure PtAl alloys exhibited oxide scale spallation and very fast oxidation rates, the Zrcontaining alloys maintained a well-adhered oxide scale and significantly lower oxidation rates.

scholarly journals Three-dimensional cellular automata modelling of cleavage propagation across crystal boundaries in polycrystalline microstructures

2015 ◽  
Vol 471 (2177) ◽  
pp. 20150039 ◽  
Author(s):  
A. Shterenlikht ◽  
L. Margetts
Keyword(s):  
Cellular Automata ◽  
Grain Boundaries ◽  
Three Dimensional ◽  
Element Model ◽  
Length Scale ◽  
Orientation Tensor ◽  
Multi Scale ◽  
Ca Model ◽  
Orientation Distributions ◽  
Crystal Boundaries

A three-dimensional cellular automata (CA) with rectilinear layout is used in this work to create and cleave polycrystalline microstructures. Each crystal is defined by a unique randomly generated orientation tensor. Separate states for grains, grain boundaries, crack flanks and crack fronts are created. Algorithms for progressive cleavage propagation through crystals and across grain boundaries are detailed. The mesh independent cleavage criterion includes the critical cleavage stress and the length scale. Resolution of an arbitrary crystallographic plane within a 26-cell Moore neighbourhood is considered. The model is implemented in Fortran 2008 coarrays. The model gives realistic predictions of grain size and mis-orientation distributions, grain boundary topology and crack geometry. Finally, we show how the proposed CA model can be linked to a finite-element model to produce a multi-scale fracture framework.

Oxidation of Experimental Ti-Si-Al Based Alloys

2016 ◽  
Vol 258 ◽  
pp. 391-394
Author(s):  
Serhii Tkachenko ◽  
Oleg Datskevich ◽  
Zdeněk Spotz ◽  
Karel Dvořák ◽  
Leonid Kulak ◽  
...  
Keyword(s):  
High Temperature ◽  
Titanium Alloys ◽  
Oxide Scale ◽  
Oxidation Kinetics ◽  
High Strength ◽  
X Ray Diffraction ◽  
Scale Thickness ◽  
Alpha Case ◽  
Good Potential ◽  
Experimental Findings

Despite the fact that conventional high temperature titanium alloys possess a good combination of low weight, high strength and good corrosion resistance, their operational temperatures do not exceed 540-600 °C, since at higher temperatures they suffer from extensive oxidation, scaling and formation of a brittle oxygen-reach diffusion layer on their surface, so-called ‘apha-case’. The alloying with silicon was regarded as a promising way to raise the working temperatures of titanium alloys, since silicon is known to improve oxidation resistance, oxide scale adherence and high temperature creep behavior of titanium without noticeable deterioration of its ductility. The present paper was focused on studying of the oxidation kinetics and the formation of oxide scale and alpha-case layers on a series of experimental Ti−Al−Si based alloys, additionally alloyed with zirconium and tin. The oxidation kinetics of the experimental alloys upon exposure in air at 700 °С for up to 240 hours was examined and compared with that of commercially available Ті−6242 alloy. The oxide scale thickness, its phase composition and crystal morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM), while the alpha-case layer was analyzed using SEM and microhardness measurements. According to the experimental findings, the experimental Ti−Al−Si based alloys demonstrated a good potential for their use at high temperatures.

A Cellular Automata Model for Nitriding of Nanocrystalline Iron

2015 ◽  
Author(s):  
Jingyi Zhao ◽  
G.-X. Wang ◽  
Yalin Dong ◽  
Chang Ye
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Cellular Automata ◽  
Grain Boundaries ◽  
Nitriding Process ◽  
Nitrogen Diffusion ◽  
Cellular Automata Model ◽  
Grain Sizes ◽  
Nanocrystalline Iron ◽  
Ca Model

In this study, a numerical model was developed to investigate the effects of grain refinement on the efficiency of nitrogen diffusion during the nitriding process. A cellular automata (CA) model without considering the effects of grain boundaries was built to simulate the nitriding process. The results from the numerical model were compared and validated by experimental data in the literature. Then, nanoscale grain boundaries were integrated into this CA model. The nitriding efficiency in materials with different grain sizes was investigated. The results demonstrate that nanocrystallization can significantly increase the nitrogen diffusion efficiency and thus make low temperature (300°C) nitriding possible.

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