TY - JOUR
T1 - Cold-rolling behavior of biomedical Ni-free Co-Cr-Mo alloys
T2 - Role of strain-induced ε martensite and its intersecting phenomena
AU - Mori, Manami
AU - Yamanaka, Kenta
AU - Chiba, Akihiko
N1 - Funding Information:
Professors Mitsuo Niinomi, Tadashi Furuhara, and Yuichiro Koizumi at the Institute for Materials Research, Tohoku University, are gratefully acknowledged for their fruitful discussion. The authors would like to thank Shun Ito, Dr. Yumiko Kodama, and Kumiko Suzuki for technical assistance. This research was financially supported by the Grant-in-Aid for Young Scientists (B) (No. 26870050 ), “Nanotechnology Platform” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, at the Center for Integrated Nanotechnology Support, Tohoku University, and the Inter-University Cooperative Research Program; the Innovative Research for Biosis-Abiosis Intelligent Interface, from the MEXT, Japan.
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2016/3
Y1 - 2016/3
N2 - Ni-free Co-Cr-Mo alloys are some of the most difficult-to-work metallic materials used commonly in biomedical applications. Since the difficulty in plastically deforming them limits their use, an in-depth understanding of their plastic deformability is of crucial importance for both academic and practical purposes. In this study, the microstructural evolution of a Co-29Cr-6Mo-0.2N (mass%) alloy during cold rolling was investigated. Further, its work-hardening behavior is discussed while focusing on the strain-induced face-centered cubic (fcc) γ→hexagonal close-packed (hcp) ε martensitic transformation (SIMT). The planar dislocation slip and subsequent SIMT occurred even in the initial stage of the deformation process owing to the low stability of the γ-phase and contributed to the work hardening behavior. However, the amount of the SIMTed ε-phase did not explain the overall variation in work hardening during cold rolling. It was found that the intersecting of the SIMTed ε-plates enhanced local strain evolution and then produced fine domain-like deformation microstructures at the intersections. Consequently, the degree of work hardening was reduced during subsequent plastic deformation, resulting in the alloy exhibiting a two-stage work hardening behavior. The results obtained in this study suggest that the interaction between ε-martensites, and ultimately its relaxation mechanism, is of significant importance; therefore, this aspect should be addressed in detail; the atomic structures of the γ-matrix/ε-martensite interfaces, the phenomenon of slip transfer at the interfaces, and the slipping behavior of the ε-phase itself are needed to be elucidated for further increasing the cold deformability of such alloys.
AB - Ni-free Co-Cr-Mo alloys are some of the most difficult-to-work metallic materials used commonly in biomedical applications. Since the difficulty in plastically deforming them limits their use, an in-depth understanding of their plastic deformability is of crucial importance for both academic and practical purposes. In this study, the microstructural evolution of a Co-29Cr-6Mo-0.2N (mass%) alloy during cold rolling was investigated. Further, its work-hardening behavior is discussed while focusing on the strain-induced face-centered cubic (fcc) γ→hexagonal close-packed (hcp) ε martensitic transformation (SIMT). The planar dislocation slip and subsequent SIMT occurred even in the initial stage of the deformation process owing to the low stability of the γ-phase and contributed to the work hardening behavior. However, the amount of the SIMTed ε-phase did not explain the overall variation in work hardening during cold rolling. It was found that the intersecting of the SIMTed ε-plates enhanced local strain evolution and then produced fine domain-like deformation microstructures at the intersections. Consequently, the degree of work hardening was reduced during subsequent plastic deformation, resulting in the alloy exhibiting a two-stage work hardening behavior. The results obtained in this study suggest that the interaction between ε-martensites, and ultimately its relaxation mechanism, is of significant importance; therefore, this aspect should be addressed in detail; the atomic structures of the γ-matrix/ε-martensite interfaces, the phenomenon of slip transfer at the interfaces, and the slipping behavior of the ε-phase itself are needed to be elucidated for further increasing the cold deformability of such alloys.
KW - Biomedical Co-Cr-Mo alloy
KW - Cold rolling
KW - Deformation microstructures
KW - Martensitic transformation
KW - Work hardening
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U2 - 10.1016/j.jmbbm.2015.10.021
DO - 10.1016/j.jmbbm.2015.10.021
M3 - Article
C2 - 26594780
AN - SCOPUS:84946923002
VL - 55
SP - 201
EP - 214
JO - Journal of the Mechanical Behavior of Biomedical Materials
JF - Journal of the Mechanical Behavior of Biomedical Materials
SN - 1751-6161
ER -