期刊
JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS
卷 29, 期 -, 页码 417-426出版社
ELSEVIER
DOI: 10.1016/j.jmbbm.2013.10.006
关键词
Biomedical Co-Cr-Mo alloys; Nitrogen addition; Microstructures; gamma -> epsilon martensitic transformation; Mechanical properties
资金
- Global COE Program Materials Integration (International Center of Education and Research), Tohoku University
- Regional Innovation Strategy Support Program, NICHe, Tohoku University
- Regional Innovation Cluster Program from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
- Grants-in-Aid for Scientific Research [13J10932] Funding Source: KAKEN
In the present study, the microstructures and tensile deformation behaviors of biomedical Co-29Cr-6Mo (wt%) alloys containing different concentrations of nitrogen (0-0.24 wt%) were systematically investigated. As the nitrogen concentration increased, the volume fraction of athermal epsilon martensite decreased, because nanoprecipitates hindered the formation of stacking faults (SFs) by acting as obstacles to Shockley partial dislocation formation, and athermal a martensite usually forms through the regular Overlapping of SFs. The formation of the athermal E martensite was completely suppressed when the nitrogen concentration exceeded 0.10 wt%, resulting in a simultaneous improvement in the strength and ductility of the alloys. It was found that the glide of the Shockley partial dislocations and, the strain-induced gamma (fcc) -> epsilon (hcp) martensitic transformation (SIMT) operated as the primary deformation mechanisms. However, adding nitrogen reduced the work hardening by suppressing the formation of the SFs and preventing the SIMT from taking place. This resulted in an intrinsic decrease in the tensile ductility of the alloys. It is also shown that all the alloys exhibited premature fractures owing to the SIMT. The formation of annealing twins in the gamma grains is found to be enhanced by nitrogen addition and to promote the SIMT, resulting in a reduction in the elongation-to-failure due to nitrogen addition. These results should aid in the design of alloys that contain nitrogen. (C) 2013 Elsevier Ltd. All rights reserved.
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