The accumulation of dislocations, which are atomic defects in materials subjected to plastic deformation, can cause structural failures. Early detection of such dislocation-related damage is essential to prevent these failures. The acoustic nonlinearity parameter β has been shown to be sensitive to the nonlinearity of dislocation motions, and prior research has shown a relationship between β and dislocation parameters in various damage mechanisms. While most work thus far reports that β generally increases with increased plastic deformation, recent research showed that β can decrease during monotonic tensile loading in stainless steel 316L characterized by in situ nonlinear ultrasonic measurements. The objective of this research is to examine the correlation between the decrease of β with plastic strain as reported in this recent study, and the initial microstructure and strain hardening rate. The initial microstructure, characterized with electron backscatter diffraction (EBSD), shows an increase in dislocation density and a reduction of grain area, which can possibly result in a decrease in β. Further, it is shown that the decrease rate of β monotonically decreases with hardening rate, providing a evidence that the decrease in β may relate to the shift from planar slip to wavy slip. These results help interpret the underlying mechanisms for the decrease in β during tensile loading.
Coarse-grained materials are widely accepted to display the highest strain hardening and the best tensile ductility. We experimentally report an attractive strain hardening rate throughout the deformation stage at 77 kelvin in a stable single-phase alloy with gradient dislocation cells that even surpasses its coarse-grained counterparts. Contrary to conventional understanding, the exceptional strain hardening arises from a distinctive dynamic structural refinement mechanism facilitated by the emission and motion of massive multiorientational tiny stacking faults (planar defects), which are fundamentally distinct from the traditional linear dislocation–mediated deformation. The dominance of atomic-scale planar deformation faulting in plastic deformation introduces a different approach for strengthening and hardening metallic materials, offering promising properties and potential applications.
more » « less- Award ID(s):
- 1809640
- PAR ID:
- 10553116
- Publisher / Repository:
- AAAS
- Date Published:
- Journal Name:
- Science
- Volume:
- 382
- Issue:
- 6667
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 185 to 190
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.adj3974
