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Modeling and Microstructure Evolution of Solid State Materials

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A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 July 2021) | Viewed by 16815

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Special Issue Editor

Prof. Dr. Kunok Chang

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Guest Editor

Kyung Hee University, Seoul, South Korea
Interests: nuclear materials; phase-field modeling; radiation damage

Special Issue Information

Dear Colleagues,

The metallic alloy microstructure is based on physical metallurgy and is known to play a key role in controlling and improving material properties.

Experimental analysis of the microstructure of metal requires equipment for various micrograph analyses, which takes a lot of effort and has a high cost.

In addition, in the novel alloy design, it is necessary to predict the microstructure according to the process conditions in advance, and the degradation of the metallic alloy may be reflected in the microstructure.

Microstructure modeling techniques such as phase-field models, kinetic Monte Carlo, and Monte Carlo Potts models have been actively used for decades to respond to these demands and have been improved towards enhancing their applicability.

Studies using the microstructural modeling of metallic systems in various fields, including Fe-based metals, Zr alloys which are widely used in the nuclear industry, lightweight materials such as Al and Ti, and super-heat-resistant alloys such as Ni alloys, are highly welcomed.

For this Special Issue in Metals, it would be great to be able to present experimental results such as TEM, EBSD, and atom probe tomography through microstructure-level modeling, and results combined with other scale modeling such as Ab initio, fracture mechanics, and CALPHAD.

Prof. Dr. Kunok Chang
Guest Editor

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Keywords

phase-field method
Monte Carlo
3D tomography
microstructure evolution
interface-driven process
diffusion-driven process

Published Papers (7 papers)

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Research

8 pages, 1194 KiB

Open AccessArticle

Effect of the Surface Roughness of Tungsten on the Sputtering Yield under Helium Irradiation: A Molecular Dynamics Study

by Hyeonho Kim, Joongseok Kwon and Kunok Chang

Metals 2021, 11(10), 1532; https://doi.org/10.3390/met11101532 - 26 Sep 2021

Cited by 2 | Viewed by 1848

Abstract

Sputtering in a divertor is one of the key phenomena that affects plasma purity and temperature. In previous experimental studies, the term sputtering yield has been used to refer to net sputtering yield, which is defined as the difference between primary sputtering yield and re-deposition. Our simulations using molecular dynamics have confirmed that both primary sputtering yield and re-deposition are affected by particle curvature. In this study, the effect of particle curvature on the net sputtering yield was quantitatively evaluated, the results were compared to existing experimental studies, and the discrepancies with experimental results were discussed. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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13 pages, 5161 KiB

Open AccessFeature PaperArticle

Effect of Sputter Deposition on the Adhesion and Failure Behavior between Cu Film and Glassy Calcium Aluminosilicate: A Molecular Dynamics Study

by Hyunhang Park and Sunghoon Lee

Metals 2021, 11(9), 1365; https://doi.org/10.3390/met11091365 - 30 Aug 2021

Viewed by 2364

Abstract

Understanding the physical vapor deposition (PVD) process of metallic coatings on an inorganic substrate is essential for the packaging and semiconductor industry. In this work, we investigate a Copper (Cu) film deposition on a glassy Calcium Aluminosilicate (CAS) by PVD and its dependence on the incident energy. Molecular dynamics simulation is adopted to mimic the deposition process, and pure Cu film is grown on top of CAS surface forming intermixing region (IR) of Cu oxide. In the initial stage of deposition, incident Cu atoms are diffused into CAS bulk and aggregated at the surface which leads to the formation of IR. When the high incident energy, 2 eV, is applied, 20% more Cu atoms are observed at the interface compared to the low incident energy, 0.2 eV, due to enhanced lateral diffusion. As the Cu film grows, the amorphous thin Cu layer of 1 nm is temporarily formed on top of CAS, and crystallization with face-centered cubic from amorphous structure follows regardless of incident energy, and surface roughness is observed to be low for high incident energy cases. Deformation and failure behavior of Cu-CAS bilayer by pulling is investigated by steered molecular dynamics technique. The adhesive failure mode is observed, which implies the bilayer experiences a failure at the interface, and a 7% higher adhesion force is predicted for the high incident energy case. To find an origin of adhesion enhancement, the distribution of Cu atoms on the fractured CAS surface is analyzed, and it turns out that 6.3% more Cu atoms remain on the surface, which can be regarded as a source for the high adhesion force. Our findings hopefully give the insight to understand deposition and failure mechanisms between heterogeneous materials and are also helping to further improve Cu adhesion in sputter experiments. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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13 pages, 31613 KiB

Open AccessArticle

Finite Element Modeling of Residual Stress at Joint Interface of Titanium Alloy and 17-4PH Stainless Steel

by Nana Kwabena Adomako, Sung Hoon Kim, Ji Hong Yoon, Se-Hwan Lee and Jeoung Han Kim

Metals 2021, 11(4), 629; https://doi.org/10.3390/met11040629 - 13 Apr 2021

Cited by 13 | Viewed by 2642

Abstract

Residual stress is a crucial element in determining the integrity of parts and lifetime of additively manufactured structures. In stainless steel and Ti-6Al-4V fabricated joints, residual stress causes cracking and delamination of the brittle intermetallic joint interface. Knowledge of the degree of residual stress at the joint interface is, therefore, important; however, the available information is limited owing to the joint’s brittle nature and its high failure susceptibility. In this study, the residual stress distribution during the deposition of 17-4PH stainless steel on Ti-6Al-4V alloy was predicted using Simufact additive software based on the finite element modeling technique. A sharp stress gradient was revealed at the joint interface, with compressive stress on the Ti-6Al-4V side and tensile stress on the 17-4PH side. This distribution is attributed to the large difference in the coefficients of thermal expansion of the two metals. The 17-4PH side exhibited maximum equivalent stress of 500 MPa, which was twice that of the Ti-6Al-4V side (240 MPa). This showed good correlation with the thermal residual stress calculations of the alloys. The thermal history predicted via simulation at the joint interface was within the temperature range of 368–477 °C and was highly congruent with that obtained in the actual experiment, approximately 300–450 °C. In the actual experiment, joint delamination occurred, ascribable to the residual stress accumulation and multiple additive manufacturing (AM) thermal cycles on the brittle FeTi and Fe₂Ti intermetallic joint interface. The build deflected to the side at an angle of 0.708° after the simulation. This study could serve as a valid reference for engineers to understand the residual stress development in 17-4PH and Ti-6Al-4V joints fabricated with AM. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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16 pages, 3507 KiB

Open AccessArticle

Effect of Al Concentration on the Microstructural Evolution of Fe-Cr-Al Systems: A Phase-Field Approach

by Jeonghwan Lee, Kwangheon Park and Kunok Chang

Metals 2021, 11(1), 4; https://doi.org/10.3390/met11010004 - 22 Dec 2020

Cited by 3 | Viewed by 1971

Abstract

In this study, the microstructural evolution of an Fe-Cr-Al system was simulated in two-dimensional (2D) and three-dimensional (3D) systems using the phase-field method. We investigated the effect of Al concentration on the microstructural evolution of the systems, with a focus on the nucleation [...] Read more.

α^{'}

phase. In addition, we quantitatively analyzed the mechanism of the effect of Al concentration on the microstructural characteristics of the 2D and 3D systems, such as the number of precipitates, average precipitate area (volume), and

α^{'}

phase fraction. In particular, we analyzed the effect of Al concentration and the dimensions of the system cell on the formation of the interconnected structure at high Cr concentrations, such as 35 Cr

a t %

and 40 Cr

a t %

. To enhance the performance of the simulations, we applied a semi-implicit Fourier spectral method for the ternary system and a parallel graphics processing unit computing technique. The results revealed that the initiation of phase separation in the 2D and 3D simulations was enhanced with an increase in the average Al concentration in the system. In addition, with an increase in the average Al concentration in both systems, the

α^{'}

phase fraction increased, while the change in the phase fraction decreased. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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9 pages, 3772 KiB

Open AccessFeature PaperArticle

Solidification and Precipitation Microstructure Simulation of a Hypereutectic Al–Mn–Fe–Si Alloy in Semi-Quantitative Phase-Field Modeling with Experimental Aid

by Jiwon Park, Chang-Seok Oh, Joo-Hee Kang, Jae-Gil Jung and Jung-Moo Lee

Metals 2020, 10(10), 1325; https://doi.org/10.3390/met10101325 - 03 Oct 2020

Cited by 2 | Viewed by 2404

Abstract

In this study, microstructural evolution during solidification of a hypereutectic Al–Mn–Fe–Si alloy was investigated using semi-quantitative two-/three-dimensional phase-field modeling. The formation of facetted Al₆Mn precipitates and the temperature evolution during solidification were simulated and experimentally validated. The temperature evolution obtained from the phase-field simulation, which was balanced between extracted heat and latent heat release, was compared to the thermal profile of the specimen measured during casting to validate the semi-quantitative phase-field simulation. The casting microstructure, grain morphology, and solute distribution of the specimen were analyzed using electron backscatter diffraction and energy-dispersive spectroscopy and compared with the simulated microstructure. The simulation results identified the different Fe to Mn ratios in Al₆(Mn_x,Fe_1−x) precipitates that formed during different solidification stages and were confirmed by energy-dispersive spectroscopy. The precipitates formed in the late solidification stage were more enriched with Fe than the primary precipitate due to solute segregation in the interdendritic channel. The semi-quantitative model facilitated a direct comparison between the simulation and experimental observations. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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10 pages, 3568 KiB

Open AccessArticle

The Effects of Inhomogeneous Elasticity and Dislocation on Thermodynamics and the Kinetics of the Spinodal Decomposition of a Fe-Cr System: A Phase-Field Study

by Wooseob Shin, Jeonghwan Lee and Kunok Chang

Metals 2020, 10(9), 1209; https://doi.org/10.3390/met10091209 - 09 Sep 2020

Viewed by 2589

Abstract

The effects of inhomogeneous elasticity and dislocation on the microstructure evolution of

α^{'}

The effects of inhomogeneous elasticity and dislocation on the microstructure evolution of

α^{'}

precipitate in a Fe-Cr system was investigated using a Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD)-type free energy incorporated phase-field method. In order to simulate the precipitation behavior by phase-field modeling in consideration of inhomogeneous elasticity, a Multiphysics Object-Oriented Simulation Environment (MOOSE) framework was used, which makes it easy to use powerful numerical means such as parallel computing and finite element method (FEM) solver. The effect of inhomogeneous elasticity due to the compositional inhomogeneity or the presence of dislocations affects the thermodynamic properties of the system was investigated, such as the lowest Cr concentration at which spinodal decomposition occurs. The effect of inhomogeneous elasticity on phase separation kinetics is also studied. Finally, we analyzed how inhomogeneous elasticity caused by compositional fluctuation or dislocation affects microstructure characteristics such as ratio between maximum precipitate size with respect to the average on early stage and later stage, respectively. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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9 pages, 1165 KiB

Open AccessArticle

Effect of Number of Variants of Zirconium Hydride on Grain Growth of Zirconium

by Bohyun Yoon and Kunok Chang

Metals 2020, 10(9), 1155; https://doi.org/10.3390/met10091155 - 27 Aug 2020

Cited by 1 | Viewed by 2213

Abstract

The microstructure characteristics of Zr-hydride in Zr are important concerns in metallurgy and nuclear engineering. In particular, it is known that the correlation between hydride and the grain boundary microstructure has a great influence on properties. In this study, a phase-field model was used to evaluate evolutions of the fractions of intra-granular and inter-granular hydride and multi-contacted hydride according to the number of structural variants of

δ

-hydride in the 3D system. The effect of the numbers of crystallographic variants of hydride on grain growth kinetics was also analyzed. We found that the pinning effect in 3D is minimized when hydrides have one crystallographic variant, which is contradictory observation with the 2D case. With grain structures with comparable average grain radii and quantities, we found that the fraction of the intra-granular and inter-granular hydrides increase as the number of crystallographic variants increases. Full article

(This article belongs to the Special Issue Modeling and Microstructure Evolution of Solid State Materials)

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