About this Abstract |
Meeting |
2024 TMS Annual Meeting & Exhibition
|
Symposium
|
Hume-Rothery Symposium on Alloy Microstructure Science and Engineering
|
Presentation Title |
3D Diffuse Scattering, Displacement Short-range Ordering, and Phonons in Pre-martensitic State |
Author(s) |
Yu U. Wang, Yongmei M. Jin |
On-Site Speaker (Planned) |
Yu U. Wang |
Abstract Scope |
Pre-martensitic phenomena occur in austenitic state prior to martensitic transformation. One prominent precursor effect is temperature-dependent diffuse scattering. We employ atomic-scale Monte Carlo simulation, phonon theory analysis, and synchrotron X-ray diffraction experiment to gain insights into 3D diffuse scattering in pre-martensitic state. A quasi-spin Ising model of ferroelastic phase transition is developed to perform the Monte Carlo simulation of thermoelastic martensitic transformation. The study focuses on the intrinsic behaviors of a defect-free crystal. It is shown that the diffuse scattering in the pre-martensitic austenite phase results from the spatial correlation of atomic-scale heterogeneous lattice displacements and manifests the displacement short-range ordering. The phenomenon is discussed in relation to transverse acoustic phonons and incomplete phonon softening, which stabilize the cubic austenite phase through increased vibrational entropy. Phonon-strain coupling and lattice stability are further analyzed using a statistical mechanics-based Gruneisen-type phonon theory. Relevant synchrotron X-ray single-crystal diffuse scattering results are also presented. |
Proceedings Inclusion? |
Planned: |
Keywords |
Other, Other, Other |