Advances in Multi-Principal Elements Alloys X: Structures and Modeling: Structures and Modeling II
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Alcoa Technical Center
Monday 2:00 PM
February 28, 2022
Room: 251B
Location: Anaheim Convention Center
Session Chair: Diana Farkas, Virginia Polytechnic Institute; Francesco Maresca, University of Groningen
2:00 PM Invited
Simulations of Deformation and Fracture in Multi-principal Element Alloys: Diana Farkas1; 1Virginia Polytechnic Institute
This talk reports multi-scale studies of deformation and fracture response in a model equi-atomic quinary high entropy FCC alloy. The simulations are based on molecular dynamics techniques at the atomistic level to study the deformation mechanisms and bridging with continuum fracture mechanics. The atomistic part is based on empirical interatomic potentials to study plasticity response for increasingly higher applied stresses. Deformation and fracture response are analyzed focusing on the role that the local composition in the random alloy plays in the deformation mechanisms. For this purpose, comparative simulations are performed with a corresponding “average atom” material that has the same average properties as the complex alloy but no local randomness. The complex high entropy alloy is both higher and has higher fracture resistance than the average atom material. These effects are analyzed in terms of dislocation nucleation and propagation mechanisms.
2:20 PM Invited
Interactions between a Dislocation and a Twin Boundary/HCP Lamella and Their Temperature Dependence in Ni-based Equiatomic Alloys: Haixuan Xu1; Sho1; 1University of Tennessee
High-entropy alloys have been under intense investigation because some of them possess superior mechanical properties to conventional alloys. For instance, FeNiCoCrMn and its subset alloys exhibit an excellent balance between strength and ductility, even at cryogenic temperatures. In this study, we investigate the interactions between dislocations and planar faults, which could also play a critical role in the enhanced ductility of these alloys. Particularly we perform atomistic simulations for the interactions between a screw dislocation and a coherent twin boundary/HCP lamella in Ni-based equiatomic alloys at various temperatures. We consider NiCo, FeNi, FeNiCo, NiCoCr, and FeNiCoCr, which are reported to possess the enhanced strength and ductility at cryogenic temperatures. The detailed interaction processes, underlying mechanisms, and their reaction stresses are investigated with a particular focus on temperature effects.
2:40 PM Invited
NOW ON-DEMAND ONLY - Theory of Yield Strength in BCC High Entropy Alloys: Francesco Maresca1; Chanho Lee2; Rui Feng2; Yi Chou3; Tamas Ungar4; Michael Widom5; Ke An6; Jonathan Poplawsky6; Yi-Chia Chou3; Peter Liaw2; William Curtin7; 1University of Groningen; 2University of Tennessee; 3National Chiao Tung University; 4Eotvos University Budapest; 5Carnegie Mellon University; 6Oak Ridge National Laboratory; 7EPFL
BCC high entropy alloys show exceptional strengths up to 1900K. Fundamental understanding of the mechanisms that control strengthening is necessary to formulate theories that enable screening over the immense compositional HEA space. Supported by the recent experimental findings in NbTaTiV and CrMoNbV alloys, we show with theory that edge dislocations can control the yield strength in BCC high entropy alloys. The theory of edge dislocation strengthening is based on the interaction of the edge dislocations with the random field of solutes in the HEAs. Theory rationalizes and captures a broad range of experiments on BCC alloys. The theory is cast in an analytical form that is parameter-free and depends on physical quantities (alloy concentrations, lattice parameter, elastic constants, misfit volumes) that can be determined ab-initio or experimentally. The reduced theory enables screening over 10 million compositions in the whole Al-Cr-Mo-Nb-Ta-W-V-Ti-Zr-Hf alloy family to find the strongest BCC HEAs.
3:00 PM
Atomistic Modeling of Diffusive High Temperature Plasticity in BCC Refractory-based MPEAs: Joel Berry1; Kate Elder1; Aurelien Perron1; 1Lawrence Livermore National Laboratory
The origins of the excellent high temperature mechanical properties of refractory-based BCC MPEAs are not well understood. At sufficiently high temperatures, plasticity in these alloys should be mediated by a mix of conservative and nonconservative defect motion, e.g. dislocation glide and climb and vacancy diffusion through the bulk and/or grain boundaries. Further, in MPEAs these processes may be significantly modulated by the complex, co-evolving compositional environment. The above effects can span multiple scales and are difficult to simultaneously incorporate into computational models. This has been one factor keeping the microstructural origins of refractory MPEA mechanical performance shrouded. We explore a way to address this issue through phenomenologically time-averaged atomistic simulation approaches (phase-field crystal) that incorporate the above effects. Simulations span from atomistic to microstructural lengths and cover experimentally relevant, diffusive times. Model development and parameterization issues will be addressed and analysis of preliminary results from simulated deformation experiments presented.