Preparation of structurally controlled dilute molybdenum-titanium alloys through a novel multi-step internal nitriding technique and their mechanical properties

Masahiro Nagae, Yoshito Takemoto, Tetsuo Yoshio, Jun Takada, Yutaka Hiraoka

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

In order to overcome the recrystallization embrittlement of molybdenum, internally nitrided dilute Mo-Ti alloy specimens having a heavily deformed surface microstructure were prepared by a novel three-step internal nitriding process at 1223-1873 K in N2 gas. Grain growth behavior and mechanical properties of nitrided specimens were investigated. Primary nitriding of the present alloys below their recrystallization temperature induced a uniform dispersion of ultrafine Ti-nitride precipitates without causing recrystallization. After secondary and tertiary nitriding, those precipitates grew into rod-like particles with a diameter of about 20 nm and a length of 50-120 nm, maintaining their deformed microstructure due to the pinning effect on grain boundary migration. The depth of the region where the recrystallization of the molybdenum matrix was suppressed was greatly dependent on the secondary nitriding temperature. The recrystallization temperature of the specimen subjected to three-step nitriding was elevated above 1873 K. The yield strength at 298 K obtained from nitrided Mo-0.5 wt% Ti alloy was about 1.6 times as high as that of the recrystallized specimen. Ductile-to-brittle transition temperature of nitrided Mo-0.5 wt% Ti alloy was about 181 K.

Original languageEnglish
Pages (from-to)50-56
Number of pages7
JournalMaterials Science and Engineering A
Volume406
Issue number1-2
DOIs
Publication statusPublished - Oct 15 2005

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molybdenum alloys
Molybdenum alloys
nitriding
Nitriding
titanium alloys
Titanium alloys
mechanical properties
Mechanical properties
preparation
Molybdenum
molybdenum
Precipitates
precipitates
microstructure
Microstructure
embrittlement
Embrittlement
yield strength
Grain growth
Nitrides

Keywords

  • Dilute Mo-Ti alloys
  • Ductile-to-brittle transition temperature
  • Multi-step internal nitriding
  • Pinning effect
  • Recrystallization temperature
  • Ti-nitride precipitate

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Preparation of structurally controlled dilute molybdenum-titanium alloys through a novel multi-step internal nitriding technique and their mechanical properties. / Nagae, Masahiro; Takemoto, Yoshito; Yoshio, Tetsuo; Takada, Jun; Hiraoka, Yutaka.

In: Materials Science and Engineering A, Vol. 406, No. 1-2, 15.10.2005, p. 50-56.

Research output: Contribution to journalArticle

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abstract = "In order to overcome the recrystallization embrittlement of molybdenum, internally nitrided dilute Mo-Ti alloy specimens having a heavily deformed surface microstructure were prepared by a novel three-step internal nitriding process at 1223-1873 K in N2 gas. Grain growth behavior and mechanical properties of nitrided specimens were investigated. Primary nitriding of the present alloys below their recrystallization temperature induced a uniform dispersion of ultrafine Ti-nitride precipitates without causing recrystallization. After secondary and tertiary nitriding, those precipitates grew into rod-like particles with a diameter of about 20 nm and a length of 50-120 nm, maintaining their deformed microstructure due to the pinning effect on grain boundary migration. The depth of the region where the recrystallization of the molybdenum matrix was suppressed was greatly dependent on the secondary nitriding temperature. The recrystallization temperature of the specimen subjected to three-step nitriding was elevated above 1873 K. The yield strength at 298 K obtained from nitrided Mo-0.5 wt{\%} Ti alloy was about 1.6 times as high as that of the recrystallized specimen. Ductile-to-brittle transition temperature of nitrided Mo-0.5 wt{\%} Ti alloy was about 181 K.",
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AB - In order to overcome the recrystallization embrittlement of molybdenum, internally nitrided dilute Mo-Ti alloy specimens having a heavily deformed surface microstructure were prepared by a novel three-step internal nitriding process at 1223-1873 K in N2 gas. Grain growth behavior and mechanical properties of nitrided specimens were investigated. Primary nitriding of the present alloys below their recrystallization temperature induced a uniform dispersion of ultrafine Ti-nitride precipitates without causing recrystallization. After secondary and tertiary nitriding, those precipitates grew into rod-like particles with a diameter of about 20 nm and a length of 50-120 nm, maintaining their deformed microstructure due to the pinning effect on grain boundary migration. The depth of the region where the recrystallization of the molybdenum matrix was suppressed was greatly dependent on the secondary nitriding temperature. The recrystallization temperature of the specimen subjected to three-step nitriding was elevated above 1873 K. The yield strength at 298 K obtained from nitrided Mo-0.5 wt% Ti alloy was about 1.6 times as high as that of the recrystallized specimen. Ductile-to-brittle transition temperature of nitrided Mo-0.5 wt% Ti alloy was about 181 K.

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