Computational Thermodynamics and Kinetics: Defects and GBs II
Sponsored by: TMS Functional Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee, TMS: Solidification Committee
Program Organizers: Hesam Askari, University Of Rochester; Damien Tourret, IMDEA Materials Institute; Eva Zarkadoula, Oak Ridge National Laboratory; Enrique Martinez Saez, Clemson University; Frederic Soisson, Cea Saclay; Fadi Abdeljawad, Lehigh University; Ziyong Hou, Chongqing University

Tuesday 8:00 AM
March 21, 2023
Room: 26A
Location: SDCC

Session Chair: Steven Kenny, Loughborough University; Ziyong Hou, Chongqing University


8:00 AM  Invited
Phase Field Modeling of Microstructures in Titanium Alloys: Benoit Appolaire1; Yann Le Bouar2; Alphonse Finel2; 1Universite de Lorraine; 2LEM CNRS-ONERA
     Beside their interest for applications requiring high specific mechanical properties and good resistance to oxydation, titanium alloys are particularly appealing for microstructure modeling because they feature a great variety of complex microstructures, ensuing from phase transformations and/or deformation. In this contribution, we will illustrate recent advances using phase field modeling in the understanding of * lengthening and thickening of alpha Widmanstatten plates, * formation of {332}<11-3> twins,* and growth of isothermal omega precipitates.

8:30 AM  
An Atomistic Approach of the Impact of Hydrogen on the Formation of Vacancy Clusters in Fcc Metals: Marie Landeiro Dos Reis1; Abdelali Oudriss1; Xavier Feaugas1; 1Lasie Cnrs Umr73
     Vacancy clusters have a major implication on multiple mechanisms (oxidation, precipitation, creep). It is thus essential to have a deep understanding of these defect stability. Multiple factors influence their formation, yet the preponderant factor seems to be the presence of a gaseous environment, like H.For this purpose, we investigate at the atomic-scale the formation of such clusters. Using empirical force fields (EAM), we show that the interaction between point-defects is attractive which favors the cluster formation. We determine their stable shape for various fcc metals: Al, Pd, Ni, Cu, Au, Ag. Finally, we show that H not only drastically decreases the formation energy and influences their stable shape but also influences the long-range elastic distortion arising to the vacancy clusters. Hence that have a direct consequence on the interaction between the clusters with dislocations and the other material defects and those impact the mechanical properties (elastic and plastic behavior).

8:50 AM  
Robustness, Sensitivity and Expressivity of Simple Many-body Potentials: Application to α-Zr: Alessandra Del Masto1; Céline Varvenne1; Jean Baccou2; Guy Tréglia1; Fabienne Ribeiro2; 1CNRS, CINaM; 2IRSN
     Interatomic potentials enable simulation of phenomena at length and time scales that outrun the capacity of most accurate ab initio approaches. Classical many-body potentials are based on physically-inspired functional forms – ensuring a reasonable transferability – and have a limited number of parameters. Their identification for a given system is crucial, but challenging. In this work, we apply model screening and sensitivity analysis techniques to get insights on the capabilities of two such potentials, focusing on irradiation defect properties of α-zirconium. The screening of the potential allows us to identify the possible artifacts related to strong gradient zones of the potential. After correction, the most influential parameters on the computed properties are identified. This suggests a sensitivity indices-oriented technique to improve existing potentials. Following this approach, we refine a potential for irradiation defects in α-Zr, thanks to a multi-objective optimization [1].[1] A.Del Masto et al., submitted (2022)

9:10 AM  
A Statistical Perspective on Embrittling Potency for Intergranular Fracture: Miguel Fernandez1; Remi Dingreville2; Douglas Spearot1; 1University of Florida; 2Sandia National Laboratories
    Embrittling potency is a thermodynamic metric that assesses the influence of solute segregation to a grain boundary on intergranular fracture. Historically, studies have reported embrittling potency as a single, scalar value for a site, assuming a particular cleavage plane. However, the topography of intergranular fracture surfaces is not generally known a priori. Accordingly, this study presents a statistical ensemble approach to compute embrittling potency, where many free surface permutations are systematically considered. The result of this approach is a statistical description of the thermodynamics of grain boundary embrittlement. As an example, this approach is implemented for the case of Cr solutes at Ni grain boundaries. A mean grain boundary embrittlement is proposed, considering both the likelihood of formation of a particular free surface and the probability of solute occupancy at each grain boundary site, to compare the relative embrittling behavior of distinct grain boundaries.

9:30 AM Break

9:50 AM  
Rationalizing the Impact of Experimental Preparation Routes on Impurity Content Using Ab-initio Phase Diagrams: Mira Todorova1; Su-Hyun Yoo1; Poulami Chakraborty1; Tilmann Hickel1; Se-Ho Kim1; Baptiste Gault1; Joerg Neugebauer1; 1Max-Planck-Insitut Fuer Eisenforschung
    Recent advances of experimental techniques with atomic resolution enable us to analyze the structure and composition of samples at the sub-nanometer scale, providing information about contamination with impurities and their distribution. Understanding the factors which govern the ingress, amount and distribution of contaminating elements, opens routes to both improving the sample quality and their utilization in targeted design to achieve a desired functionality. Using an ab-initio based thermodynamic approach and surface phase diagrams we unravel the impact of preparation conditions on experimental observations and materials properties. The power and the performance of these ab-initio based thermodynamic concepts will be highlighted using as examples impurity incorporation during wet-synthesis of nano-aerogels [JACS 144, 987 (2022); Adv. Mater. 2203030 (2022)] and the origin of the H signal in Atom Probe Tomorgraphy measurements of alkali and transition metals [New J. Phys. 24, 013008 (2022)].

10:10 AM  
Handling Conditional Convergence in Point Defect Calculations: Celine Varvenne1; Emmanuel Clouet2; Thomas Jourdan2; 1CINaM, CNRS, Aix-Marseille Univ.; 2Université Paris-Saclay, CEA
    Periodic Boundary Conditions are very popular for numerical simulations, but induce artifacts when computing properties of point defects, small clusters or dislocation loops. Their long range elastic fields quantitatively impact the convergence rate and the accuracy of both ab initio calculations of isolated point defect energetics and mesoscopic simulations of ensembles of point defects. Getting rid of these artifacts requires the computation of infinite conditionally convergent sums. Here, we first show the formal equivalence between various numerical regularization techniques of the literature that are based on summations in real space. We then discuss the direct construction of physically-acceptable solutions for the elastic fields in reciprocal space. Accuracy and numerical efficiency of all schemes are compared on metals and defects having various crystalline structures / point symmetries: several SIAs configurations in hcp Zr, and carbon solute in fcc Ni. We finally discuss cases of constant stress/constant strain calculations and linear defects.

10:30 AM  Invited
Atomistic Modelling of Thin Film Growth: Steven Kenny1; 1Loughborough University
     The coating of materials with thin films has applications in numerous areas . This work will highlight the use of modelling applied to thin films used on glazing to achieve energy demand reduction. This work will discuss the growth of one of the critical areas within the low emissivity coatings, the interface between silver and the transparent conducting oxide. . These systems will be used to illustrate the power of these methods in identifying very complicated growth processes that are critical in these materials. We will show how the models can help understand the role of experimental parameters such as deposition energy, the arriving species and Argon co-deposition on the morphology of the films. To achieve simulations on these systems that realistically model the experimental processes new modelling techniques have been developed to allow the modelling over realistic timescales.