Related Experiment Video
Updated: Oct 3, 2025

Determining the Mechanical Strength of Ultra-Fine-Grained Metals
Published on: November 22, 2021
Nontrivial nanostructure, stress relaxation mechanisms, and crystallography for pressure-induced Si-I → Si-II phase
Hao Chen1, Valery I Levitas2,3, Dmitry Popov4
1Key Laboratory of Pressure Systems and Safety, Ministry of Education, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, People's Republic of China.
Abstract:
Crystallographic theory based on energy minimization suggests austenite-twinned martensite interfaces with specific orientation, which are confirmed experimentally for various materials. Pressure-induced phase transformation (PT) from semiconducting Si-I to metallic Si-II, due to very large and anisotropic transformation strain, may challenge this theory. Here, unexpected nanostructure evolution during Si-I → Si-II PT is revealed by combining molecular dynamics (MD), crystallographic theory, generalized for strained crystals, and in situ real-time Laue X-ray diffraction (XRD). Twinned Si-II, consisting of two martensitic variants, and unexpected nanobands, consisting of alternating strongly deformed and rotated residual Si-I and third variant of Si-II, form [Formula: see text] interface with Si-I and produce almost self-accommodated nanostructure despite the large transformation volumetric strain of [Formula: see text]. The interfacial bands arrest the [Formula: see text] interfaces, leading to repeating nucleation-growth-arrest process and to growth by propagating [Formula: see text] interface, which (as well as [Formula: see text] interface) do not appear in traditional crystallographic theory.
Related Concept Videos
Transformation of Plane Stress
Phase Transitions
Phase Transitions: Sublimation and Deposition
Phase Diagram

