ICME 2023: Linkages: Microstructure III
Program Organizers: Charles Ward, AFRL/RXM; Heather Murdoch, U.S. Army Research Laboratory
Wednesday 3:20 PM
May 24, 2023
Room: Caribbean VI & VII
Location: Caribe Royale
Session Chair: Lang Yuan, University of South Carolina
3:20 PM
Microstructure Informed Modelling of Ductile-to-brittle Transition in Ferritic Steels: Sicong Ren1; Bernard Marini2; Pierre Forget2; Matti Lindroos1; Anssi Laukkanen1; 1VTT Technical Research Centre of Finland Ltd.; 2CEA Paris-Saclay
The embrittlement of reactor pressure vessel (RPV) steel has been a great concern of the nuclear industry. Macro-segregated areas of carbon, alloy elements and impurities occur due to uneven solidification rates at different locations during the heavy forging process. These heterogeneities can lead to significant variations in fracture toughness in the Ductile-to-Brittle Transition (DBT) region. To quantitatively assess the safety of RPV, advanced micromechanical tools combining crystal plasticity and the local approach to fracture (LAF) are developed. This multiscale approach is applied to laboratory steels with different segregation levels chemically representative of actual RPV components. Simulation results demonstrate that the current approach is capable of predicting the shift of the DBT zone and the statistical scatter of fracture toughness with the variation of alloying elements. Results give insights into factors affecting fracture properties. Comparisons to phase field damage methods and new model prospects towards more accurate predictions are also discussed.
3:40 PM
Enabling Molecular Dynamics Simulations of Helium Bubble Formation in Tritium-containing Austenitic Stainless Steels: An Fe-Ni-Cr-H-He Potential: Xiaowang Zhou1; Michael Foster1; Ryan Sills2; 1Sandia National Laboratories; 2Rutgers University
Helium bubbles impact mechanical properties of nuclear materials. An Fe-Ni-Cr-H-He potential has been developed to enable molecular dynamics simulations of helium bubble nucleation and growth. This is accomplished by addressing three challenging paradoxes: (a) helium forms tightly bound dimers and clusters in the lattice but are only bound by weak van de Waals forces in the gas phase, (b) helium diffuses readily in metals yet significantly distort the lattice causing large volume expansions; (c) helium prefers tetrahedral interstitial sites to the larger octahedral sites despite strong repulsion from metal atoms. Our potential reproduces quantum mechanical results on relevant properties to bubble nucleation and growth. In addition to validation by static properties, molecular dynamics simulations establish that our potential enables the nucleation of helium bubbles from an initial random distribution of He interstitial atoms while at the same time capturing the equation of state in the pure He phase.
4:00 PM
Multi-scale Microstructure Evolution Informed Constitutive Behavior Modeling of Cast Iron: Ujjal Tewary1; Shyamprasad Karagadde2; Alankar Alankar2; Goutam Mohapatra1; Satyam Sahay1; Indradev Samajdar2; 1John Deere India Pvt. Ltd.; 2Indian Institute of Technology Bombay
Cast iron is one of the oldest materials known to humankind. A microstructure of cast iron exhibits different morphologies of graphite that range from flake to compacted to spheroidal particles. The morphology is controlled by magnesium addition during the solidification process. Though this technology dates back several decades, the exact mechanism of shape change remains debatable. This study used a combination of industrial casting trials, analytical microscopy, and molecular dynamics simulation to understand the origin of graphite morphology in cast iron. Further, from this theoretical premise, an integrated multi-scale model of coupled heat transfer and phase transformation during the solidification of different types of cast irons was developed and validated with experimental results. Finally, constitutive models were developed for studying the microstructure-property correlations. Thus, this study provided an appropriate example of an integrated computational multi-scale modeling approach of simulating a casting, predicting solidified microstructure, and obtaining structure-property correlations.