Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment

Ueki, Kosuke; Abe, Mai; Ueda, Kyosuke; Nakai, Masaaki; Nakano, Takayoshi; Narushima, Takayuki

doi:https://doi.org/10.1016/j.msea.2018.10.016

Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment

Ueki, Kosuke; Abe, Mai; Ueda, Kyosuke et al.

Materials Science and Engineering A, 2019, 739, 53-61

Number of Access:480（2025-08-21 04:36 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/89827

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Title	Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment
Creator	NRID 1000010845928 1000010845928 CreatorName Ueki, Kosuke
	CreatorName Abe, Mai
	NRID 1000040507901 1000040507901 CreatorName Ueda, Kyosuke
	NRID 1000020431603 1000020431603 CreatorName Nakai, Masaaki
	NRID 1000030243182 1000030243182 ORCID 0000-0001-8052-1698 0000-0001-8052-1698 researchmap permalink read0013987 read0013987 Scopus Author ID 7403896013 7403896013 CreatorName Nakano, Takayoshi
	NRID 1000020198394 1000020198394 CreatorName Narushima, Takayuki
Subject	Heat treatment
	Mechanical properties
	Plastic deformation
	Stacking fault
	Strain-induced martensitic transformation
Description	Ueki K., Abe M., Ueda K., et al. Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment. Materials Science and Engineering A, 739, 53. https://doi.org/10.1016/j.msea.2018.10.016.
Abstract	The microstructure and tensile properties of Co–27Cr–6Mo (mass%) alloys heat-treated at 673–1373 K were studied. Lower elongation was observed after heat treatment at 1073 K due to formation of carbonitride precipitates. In contrast, when low-temperature heat treatment (LTHT) was applied at 673–873 K, both the ultimate tensile strength and elongation synchronously improved compared with the solution-treated alloy. Electron backscatter diffraction analysis for plastic-strained alloys and in situ X-ray diffraction analysis under stress-induced conditions revealed that the strain-induced martensitic transformation (SIMT) of the γ(fcc)-phase to ε(hcp)-phase during plastic deformation was suppressed by the LTHT. Stacking faults (thin ε-phase) were observed to collide in the LTHT alloys. The following mechanisms for the synchronous improvement in the tensile strength and elongation after LHTH are proposed. First, stacking faults with multiple variants were formed during LTHT. Then, the ε-phase of a single variant formed by SIMT during plastic deformation collides with preexisting multi-variant stacking faults formed during LTHT, increasing the tensile strength. In addition, the SIMT during plastic deformation is suppressed in the high-plastic-strain region by the collision. This decreases the total amount of ε-phase formed during plastic deformation, which improves the ductility. We demonstrated that LTHT of Co–Cr–Mo alloys effectively improves the performance and mechanical safety of spinal fixation implants, which often fracture because of fatigue cracking.
Publisher	Elsevier
Source Title	Materials Science and Engineering A
Volume (Issue)	739
Page	53-61
Date of Issued	2019-01-02
Language	English
Handle URL	https://hdl.handle.net/11094/89827
PISSN	09215093
NCID	AA10720420
Relation.isIdenticalTo	DOI (Publisher Version) https://doi.org/10.1016/j.msea.2018.10.016
Access Rights	open access
CopyRight	This article is licensed under a Creative Commons Attribution 4.0 International License.
oaire:version	Version of Record
Category	学術雑誌論文 Journal Article

Resource Type	journal article
Local Type	Journal Article
DCMI Type	Text
DCTERMS.bibliographicCitation	Materials Science and Engineering A. 2019, 739, p. 53-61
DC.title	Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment
DC.creator	Ueki, Kosuke
	Abe, Mai
	Ueda, Kyosuke
	Nakai, Masaaki
	Nakano, Takayoshi
	Narushima, Takayuki
DC.publisher	Elsevier
DC.language' scheme='DCTERMS.RFC1766	English
DC.type' scheme='DCTERMS.DCMIType	Text
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2019-01-02
DC.identifier	https://doi.org/10.1016/j.msea.2018.10.016
DC.subject	Heat treatment
	Mechanical properties
	Plastic deformation
	Stacking fault
	Strain-induced martensitic transformation
DC.description	Ueki K., Abe M., Ueda K., et al. Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment. Materials Science and Engineering A, 739, 53. https://doi.org/10.1016/j.msea.2018.10.016.
DCTERMS.abstract	The microstructure and tensile properties of Co–27Cr–6Mo (mass%) alloys heat-treated at 673–1373 K were studied. Lower elongation was observed after heat treatment at 1073 K due to formation of carbonitride precipitates. In contrast, when low-temperature heat treatment (LTHT) was applied at 673–873 K, both the ultimate tensile strength and elongation synchronously improved compared with the solution-treated alloy. Electron backscatter diffraction analysis for plastic-strained alloys and in situ X-ray diffraction analysis under stress-induced conditions revealed that the strain-induced martensitic transformation (SIMT) of the γ(fcc)-phase to ε(hcp)-phase during plastic deformation was suppressed by the LTHT. Stacking faults (thin ε-phase) were observed to collide in the LTHT alloys. The following mechanisms for the synchronous improvement in the tensile strength and elongation after LHTH are proposed. First, stacking faults with multiple variants were formed during LTHT. Then, the ε-phase of a single variant formed by SIMT during plastic deformation collides with preexisting multi-variant stacking faults formed during LTHT, increasing the tensile strength. In addition, the SIMT during plastic deformation is suppressed in the high-plastic-strain region by the collision. This decreases the total amount of ε-phase formed during plastic deformation, which improves the ductility. We demonstrated that LTHT of Co–Cr–Mo alloys effectively improves the performance and mechanical safety of spinal fixation implants, which often fracture because of fatigue cracking.
DC.rights	This article is licensed under a Creative Commons Attribution 4.0 International License.
DC.format	89827
citation_title	Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment
citation_author	Ueki, Kosuke
	Abe, Mai
	Ueda, Kyosuke
	Nakai, Masaaki
	Nakano, Takayoshi
	Narushima, Takayuki
citation_publisher	Elsevier
citation_language	English
citation_date	2019-01-02
citation_journal_title	Materials Science and Engineering A
citation_volume	739
citation_firstpage	53
citation_lastpage	61
citation_doi	https://doi.org/10.1016/j.msea.2018.10.016
citation_public_url	https://hdl.handle.net/11094/89827

Synchronous improvement in strength and ductility of biomedical Co–Cr–Mo alloys by unique low-temperature heat treatment

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