Journal
NATURE
Volume 579, Issue 7797, Pages 67-+Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/s41586-020-2036-z
Keywords
-
Categories
Funding
- National Natural Science Foundation of China (NSFC) [11621062, 11772294, U1530402, 11811530001]
- Fundamental Research Funds for the Central Universities of China [2018XZZX001-05]
- NSF [EAR-1654687]
- National Key Research and Development Program of China [2016YFB0700400]
- DOE Office of Science User Facility [DE-AC02-05CH11231]
- COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF [EAR 1606856]
- CDAC
Ask authors/readers for more resources
High-pressure diamond anvil cell experiments reveal that compression strengthening of nanocrystalline nickel increases as its grain sizes decrease to 3 nanometres, owing to dislocation hardening and suppression of grain boundary plasticity. The Hall-Petch relationship, according to which the strength of a metal increases as the grain size decreases, has been reported to break down at a critical grain size of around 10 to 15 nanometres(1,2). As the grain size decreases beyond this point, the dominant mechanism of deformation switches from a dislocation-mediated process to grain boundary sliding, leading to material softening. In one previous approach, stabilization of grain boundaries through relaxation and molybdenum segregation was used to prevent this softening effect in nickel-molybdenum alloys with grain sizes below 10 nanometres(3). Here we track in situ the yield stress and deformation texturing of pure nickel samples of various average grain sizes using a diamond anvil cell coupled with radial X-ray diffraction. Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening enhanced (rather than reduced) at grain sizes smaller than 20 nanometres. We achieve a yield strength of approximately 4.2 gigapascals in our 3-nanometre-grain-size samples, ten times stronger than that of a commercial nickel material. A maximum flow stress of 10.2 gigapascals is obtained in nickel of grain size 3 nanometres for the pressure range studied here. We see similar patterns of compression strengthening in gold and palladium samples down to the smallest grain sizes. Simulations and transmission electron microscopy reveal that the high strength observed in nickel of grain size 3 nanometres is caused by the superposition of strengthening mechanisms: both partial and full dislocation hardening plus suppression of grain boundary plasticity. These insights contribute to the ongoing search for ultrastrong metals via materials engineering.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available