University of Oulu

C.Y. Hu, M.C. Somani, R.D.K. Misra, C.G. Yang, The significance of phase reversion-induced nanograined/ultrafine-grained structure on the load-controlled deformation response and related mechanism in copper-bearing austenitic stainless steel, Journal of the Mechanical Behavior of Biomedical Materials, Volume 104, 2020, 103666, ISSN 1751-6161,

The significance of phase reversion-induced nanograined/ultrafine-grained structure on the load-controlled deformation response and related mechanism in copper-bearing austenitic stainless steel

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Author: Hu, C.Y.1; Somani, M.C.2; Misra, R.D.K.1;
Organizations: 1Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, 500 W. University Avenue, University of Texas at El Paso, El Paso, TX, 79968, USA
2Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, FI-90014, Oulu, Finland
3Institute of Metal Research, 72 Wenhua Road, Chinese Academy of Science, Shenyang, 110016, China
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.8 MB)
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Language: English
Published: Elsevier, 2020
Publish Date: 2022-01-31


The ingenious concept of phase reversion annealing involving cold deformation of parent austenite to strain-induced martensite, followed by annealing was used to obtain nano-grained/ultrafine-grained (NG/UFG) structure in a Cu-bearing biomedical austenitic stainless steel resulting in high strength-high ductility combination. Having employed the concept effectively, the primary objective of this study is to critically analyze the interplay between the load-controlled deformation response, strain-rate sensitivity and deformation mechanism of NG/UFG austenitic stainless steel via nanoscale deformation experiments and compare with its coarse-grained (CG) counterpart. The study demonstrated that the strain-rate sensitivity of NG/UFG was ~1.5 times that of the CG structure. Post-mortem electron microscopy of plastic zone surrounding the indents indicated that the active deformation mechanism was nanoscale twinning with typical characteristics of a network of intersecting twins in the NG/UFG structure, while strain-induced martensite transformation was the effective deformation mechanism for the CG structure. The fracture morphology was also different for the two steels, essentially ductile in nature, and was characterized by striations marking the line-up of voids in NG/UFG steel and microvoid coalescence in CG counterpart. The differences in deformation mechanisms between the NG/UFG and CG structure are attributed to the austenite stability — strain energy relationship. Furthermore, the presence of ~3 wt % Cu in austenitic stainless steel had somewhat moderate effect on strain-rate sensitivity and activation volume at similar level of grain size in its Cu-free counterpart. Specifically, in the NG/UFG structure, the nanoscale twin density was noticeably higher in Cu-bearing austenitic stainless steel as compared to Cu-free counterpart, as Cu is known to increase the stacking fault energy.

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Series: Journal of the mechanical behavior of biomedical materials
ISSN: 1751-6161
ISSN-E: 1878-0180
ISSN-L: 1751-6161
Volume: 104
Article number: 103666
DOI: 10.1016/j.jmbbm.2020.103666
Type of Publication: A1 Journal article – refereed
Field of Science: 217 Medical engineering
216 Materials engineering
Funding: R.D.K. Misra gratefully acknowledges financial support from the National Science Foundation, USA through grant number DMR 1602080. M.C. Somani would like to express his gratitude to the Academy of Finland for allowing him to conduct this research under the auspices of the Genome of Steel (Profi3) through project #311934.
Copyright information: © 2020 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license