Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations

Tane, Masakazu; Nishiyama, Hiroki; Umeda, Akihiro; Okamoto, Norihiko L.; Inoue, Koji; Luckabauer, Martin; Nagai, Yasuyoshi; Sekino, Tohru; Nakano, Takayoshi; Ichitsubo, Tetsu

doi:https://doi.org/10.1103/PhysRevMaterials.3.043604

Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations

Tane, Masakazu; Nishiyama, Hiroki; Umeda, Akihiro et al.

Physical Review Materials, 2019, 3(4)

Number of Access:790（2025-08-16 00:37 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/89929

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Title	Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations
Creator	NRID 1000080379099 1000080379099 CreatorName Tane, Masakazu
	CreatorName Nishiyama, Hiroki
	CreatorName Umeda, Akihiro
	NRID 1000060505692 1000060505692 CreatorName Okamoto, Norihiko L.
	CreatorName Inoue, Koji
	CreatorName Luckabauer, Martin
	NRID 1000010302209 1000010302209 CreatorName Nagai, Yasuyoshi
	NRID 1000020226658 1000020226658 ORCID 0000-0002-6605-9166 0000-0002-6605-9166 researchmap permalink tohrusekino tohrusekino Scopus Author ID 7006706950 7006706950 CreatorName Sekino, Tohru
	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 1000040324826 1000040324826 CreatorName Ichitsubo, Tetsu
Description	Tane M., Nishiyama H., Umeda A., et al. Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations. Physical Review Materials 3, 043604 (2019); https://doi.org/10.1103/PhysRevMaterials.3.043604.
Abstract	In titanium alloys, the ω(hexagonal)-phase transformation has been categorized as either a diffusion-mediated isothermal transformation or an athermal transformation that occurs spontaneously via a diffusionless mechanism. Here we report a diffusionless isothermal ω transformation that can occur even above the ω transformation temperature. In body-centered cubic β-titanium alloyed with β-stabilizing elements, there are locally unstable regions having fewer β-stabilizing elements owing to quenched-in compositional fluctuations that are inevitably present in thermal equilibrium. In these locally unstable regions, diffusionless isothermal ω transformation occurs even when the entire β region is stable on average so that athermal ω transformation cannot occur. This anomalous, localized transformation originates from the fluctuation-driven localized softening of 2/3[111]β longitudinal phonon, which cannot be suppressed by the stabilization of β phase on average. In the diffusionless isothermal and athermal ω transformations, the transformation rate is dominated by two activation processes: a dynamical collapse of {111}β pairs, caused by the phonon softening, and a nucleation process. In the diffusionless isothermal transformation, the ω-phase nucleation, resulting from the localized phonon softening, requires relatively high activation energy owing to the coherent β/ω interface. Thus, the transformation occurs at slower rates than the athermal transformation, which occurs by the widely spread phonon softening. Consequently, the nucleation probability reflecting the β/ω interface energy is the rate-determining process in the diffusionless ω transformations.
Publisher	American Physical Society
Source Title	Physical Review Materials
Volume (Issue)	3(4)
Date of Issued	2019-04-16
Language	English
Handle URL	https://hdl.handle.net/11094/89929
eISSN	24759953
Relation.isIdenticalTo	DOI (Publisher Version) https://doi.org/10.1103/PhysRevMaterials.3.043604
Access Rights	open access
CopyRight	Copyright (2019) by the American Physical Society
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	Physical Review Materials. 2019, 3(4)
DC.title	Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations
DC.creator	Tane, Masakazu
	Nishiyama, Hiroki
	Umeda, Akihiro
	Okamoto, Norihiko L.
	Inoue, Koji
	Luckabauer, Martin
	Nagai, Yasuyoshi
	Sekino, Tohru
	Nakano, Takayoshi
	Ichitsubo, Tetsu
DC.publisher	American Physical Society
DC.language' scheme='DCTERMS.RFC1766	English
DC.type' scheme='DCTERMS.DCMIType	Text
DCTERMS.issued' scheme='DCTERMS.W3CDTF	2019-04-16
DC.identifier	https://doi.org/10.1103/PhysRevMaterials.3.043604
DC.description	Tane M., Nishiyama H., Umeda A., et al. Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations. Physical Review Materials 3, 043604 (2019); https://doi.org/10.1103/PhysRevMaterials.3.043604.
DCTERMS.abstract	In titanium alloys, the ω(hexagonal)-phase transformation has been categorized as either a diffusion-mediated isothermal transformation or an athermal transformation that occurs spontaneously via a diffusionless mechanism. Here we report a diffusionless isothermal ω transformation that can occur even above the ω transformation temperature. In body-centered cubic β-titanium alloyed with β-stabilizing elements, there are locally unstable regions having fewer β-stabilizing elements owing to quenched-in compositional fluctuations that are inevitably present in thermal equilibrium. In these locally unstable regions, diffusionless isothermal ω transformation occurs even when the entire β region is stable on average so that athermal ω transformation cannot occur. This anomalous, localized transformation originates from the fluctuation-driven localized softening of 2/3[111]β longitudinal phonon, which cannot be suppressed by the stabilization of β phase on average. In the diffusionless isothermal and athermal ω transformations, the transformation rate is dominated by two activation processes: a dynamical collapse of {111}β pairs, caused by the phonon softening, and a nucleation process. In the diffusionless isothermal transformation, the ω-phase nucleation, resulting from the localized phonon softening, requires relatively high activation energy owing to the coherent β/ω interface. Thus, the transformation occurs at slower rates than the athermal transformation, which occurs by the widely spread phonon softening. Consequently, the nucleation probability reflecting the β/ω interface energy is the rate-determining process in the diffusionless ω transformations.
DC.rights	Copyright (2019) by the American Physical Society
DC.format	89929
citation_title	Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations
citation_author	Tane, Masakazu
	Nishiyama, Hiroki
	Umeda, Akihiro
	Okamoto, Norihiko L.
	Inoue, Koji
	Luckabauer, Martin
	Nagai, Yasuyoshi
	Sekino, Tohru
	Nakano, Takayoshi
	Ichitsubo, Tetsu
citation_publisher	American Physical Society
citation_language	English
citation_date	2019-04-16
citation_journal_title	Physical Review Materials
citation_volume	3
citation_issue	4
citation_doi	https://doi.org/10.1103/PhysRevMaterials.3.043604
citation_public_url	https://hdl.handle.net/11094/89929

Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations

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