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Study of the plastic flow, strain-induced phase transformations (PTs), and nanostructure evolution under high pressure is important for producing new nanostructured phases and understanding physical processes. However, these processes depend on an unlimited combination of five plastic strain components and an entire strain path with no hope of fully comprehending. Here, we introduce the rough diamond anvils (rough-DA) to reach maximum friction equal to the yield strength in shear, which allows determination of pressure-dependent yield strength. We apply rough-DA to compression of severely pre-deformed Zr. We found in situ that after severe straining, crystallite size and dislocation density of α and ω-Zr are getting pressure-, strain- and strain-path-independent, reach steady values before and after PT, and depend solely on the volume fraction of ω-Zr during PT. Immediately after completing PT, ω-Zr behaves like perfectly plastic, isotropic, and strain-path-independent. Rough-DA produces a steady nanostructure in α-Zr with lower crystallite size and larger dislocation density than smooth diamonds. This leads to a record minimum pressure (0.67 GPa) for α-ω PT. Kinetics of strain-induced PT, in addition to plastic strain, unexpectedly depends on time. The obtained results significantly enrich the fundamental understanding of plasticity, PTs, and nanostructure, and create new opportunities in material design, synthesis, and processing of nanostructured materials by coupling severe plastic deformations and PT at low pressure.
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This content will become publicly available on May 1, 2026
Steady states in severe plastic deformations and microstructure at normal and high pressure
The main fundamental problem in studying plasticity and microstructure evolution is that they depend on five components of the plastic strain tensor εp , its entire path εp , and pressure p and its path p , which leaves little hope of finding some general laws, especially at severe plastic straining and high pressures. Here, we review the validity of the following hypothesis for quasi-static material behavior after some critical level of cold severe plastic strain and some straining paths: initially isotropic polycrystalline materials behave like perfectly plastic, isotropic, and strain-path-independent with the corresponding limit surface of perfect plasticity and reach steady values of the crystallite/grain size and dislocation density, which are strain- and strain-path-independent. However, there are multiple steady microstructural states and corresponding limit surfaces of perfect plasticity. The main challenge is to find for which classes of loading paths ε path p path and p material behaves along the same limit surface of perfect plasticity and steady microstructural state and for which loading paths p path ε path p and there is a jump to the different limit surface of perfect plasticity and steady microstructural state. Various experimental, computational, and coupled experimental-computational techniques are analyzed, and some controversies and challenges are summarized.
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- Award ID(s):
- 2246991
- PAR ID:
- 10588550
- Publisher / Repository:
- ELSEVIER
- Date Published:
- Journal Name:
- Journal of Materials Research and Technology
- Volume:
- 36
- Issue:
- C
- ISSN:
- 2238-7854
- Page Range / eLocation ID:
- 382 to 397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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