Interfaces and Phase Transformations: Interfaces and Phase Transformation I
Sponsored by: TMS Phase Transformations Committee
Program Organizers: Arun Devaraj, Pacific Northwest National Laboratory; Matthias Militzer, University of British Columbia; Matthew Steiner, University of Cincinnati; Mohsen Zaeem, Colorado School of Mines; Yufeng Zheng, University of North Texas
Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 37
Location: MS&T Virtual
Session Chair: ARUN DEVARAJ, Pacific Northwest National Laboratory; yufeng Zheng, University of Reno Nevada
2:00 PM Invited
Localized Phase Transformation at Interfaces – A New Alloy Design Strategy: Longsheng Feng1; Ashton Egan1; Qianglong Liang1; Yipeng Gao2; Michael Mills1; Yunzhi Wang1; 1Ohio State University; 2INL
Homophase and heterophase interfaces in materials have been engineered well over a century through various simple and sophisticated processing techniques to achieve special properties. In structural materials, these interfaces have been utilized effectively to regulate dislocation, twinning and cracking activities and hence to control the strengthening and toughening behaviors. In this presentation, however, we will show a different way of utilizing these interfaces in alloy design. In particular, by using a combination CALPHAD, phase transition graph (PTG) and phase-field approaches, we demonstrate how homophase interfaces such as stacking faults and deformation twin boundaries alter phase equilibria and harbor localized phase transformations, which allows one to achieve superior high-temperature work-hardening ability and creep performance in Ni-base superalloys, and ultralow modulus and non-hysteretic and linear superelasticity in NiTi shape memory alloys. This work is supported by NSF/DMREF program and DOE/BES program.
2:40 PM
A Phase Field Dislocation Dynamics Model in Heterogeneous Crystalline Media: Shuozhi Xu1; Irene Beyerlein1; 1University of California, Santa Barbara
Understanding dislocation dynamics in heterogeneous crystalline media necessitates modeling of plastic deformation in the vicinity of traction-free surfaces and interfaces. For example, in metals, voids, grain boundaries, and bimetal interfaces can impede dislocation gliding and hence contribute to strain hardening. While the atomistic simulation method is desirable in modeling dislocation dynamics in these cases, the simulation cells are usually at the nano-scale due to the high computational cost. Here, we develop a phase-field dislocation dynamics (PFDD) model that takes into account free surfaces and interfaces by employing Eshelby’s equivalent inclusion method. In this model, the heterogeneities with a general geometry and plastic deformation on general slip planes progress hand in hand. We use the PFDD model to study static dislocations in adjacent to surfaces/interfaces as well as slip interactions between dislocation and voids/interfaces. Simulation results are benchmarked against atomistic simulations and analytical solutions.