Next Article in Journal
Assessment of Silica Recovery from Metallurgical Mining Waste, by Means of Column Flotation
Previous Article in Journal
Cold-Rolling Strain Hardening Effect on the Microstructure, Serration-Flow Behaviour and Dislocation Density of Friction Stir Welded AA5083
Open AccessArticle

Precipitation during γ-ε Phase Transformation in Biomedical Co-Cr-Mo Alloys Fabricated by Electron Beam Melting

1
Department of Mechanical Engineering, Faculty of Science and Engineering, Kindai University, 3-4-1, Kowakae, Higashiosaka 577-8502, Japan
2
Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02, Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan
3
Division of Materials Science and Engineering, Graduate School of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871, Japan
4
Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan
5
Research Center for Structural Materials, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 71; https://doi.org/10.3390/met10010071
Received: 25 November 2019 / Revised: 23 December 2019 / Accepted: 25 December 2019 / Published: 2 January 2020
We studied the precipitates that were induced during γ-ε phase transformation in biomedical Co-28Cr-6Mo (mass%) alloys that were fabricated by electron beam melting with carbon contents of 0.184 and 0.018 mass%. In the high-C as-built alloy, M23X6-type, π-phase (M3T2X-type), and η-phase (M6X-M12X-type) precipitates were observed (M and T: metallic elements, X: C and/or N). σ-phase (Co(Cr,Mo)), π-phase, and Co3Mo2Si-type precipitates were observed in the low-C as-built alloy. This is the first report that shows the presence and chemical composition of this precipitate, as the Co3Mo2Si-type precipitate has not been detected in biomedical Co-Cr-Mo alloys before. After aging in the ε-phase stability region, the high-C and low-C alloys both contained a single ε-phase matrix, and the amount of π-phase precipitates increased. Conversely, the amount of π-phase precipitates in both alloys decreased when a reverse transformation treatment was applied in the γ-phase stability region after aging. In the low-C alloy, the amount of Co3Mo2Si-type precipitates increased after reverse transformation treatment. These results indicate that the dissolution of π-phase precipitates and the formation of Co3Mo2Si-type precipitates during reverse transformation promote the formation of fine γ-phase grains at the precipitate/ε-phase matrix interface, because the formation and dissolution of these precipitates affect the γ-phase stability of the matrix. View Full-Text
Keywords: Co-Cr-Mo alloy; additive manufacturing; heat treatment; reverse transformation treatment Co-Cr-Mo alloy; additive manufacturing; heat treatment; reverse transformation treatment
Show Figures

Figure 1

MDPI and ACS Style

Ueki, K.; Kasamatsu, M.; Ueda, K.; Koizumi, Y.; Wei, D.; Chiba, A.; Narushima, T. Precipitation during γ-ε Phase Transformation in Biomedical Co-Cr-Mo Alloys Fabricated by Electron Beam Melting. Metals 2020, 10, 71.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop