TY - JOUR
T1 - Preparation of structurally controlled dilute molybdenum-titanium alloys through a novel multi-step internal nitriding technique and their mechanical properties
AU - Nagae, Masahiro
AU - Takemoto, Yoshito
AU - Yoshio, Tetsuo
AU - Takada, Jun
AU - Hiraoka, Yutaka
N1 - Funding Information:
The authors are grateful to I. Sato and T. Fukumitsu for their assistance with experiments and to Dr. H. Kuwahara (Research Institute for Applied Science, Kyoto, Japan) and Dr. M. Maki (Kyoto University, Kyoto, Japan) for helpful discussions. We are greatly indebted to A.L.M.T. TECH Inc. for supplying Mo–Ti alloys. This study was partly supported by a Grant-in-Aid for Encouragement of Young Scientists and a Grant-in-Aid for JSPS Fellows from Japan Society for the Promotion of Science.
PY - 2005/10/15
Y1 - 2005/10/15
N2 - 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.
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.
KW - Dilute Mo-Ti alloys
KW - Ductile-to-brittle transition temperature
KW - Multi-step internal nitriding
KW - Pinning effect
KW - Recrystallization temperature
KW - Ti-nitride precipitate
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U2 - 10.1016/j.msea.2005.06.039
DO - 10.1016/j.msea.2005.06.039
M3 - Article
AN - SCOPUS:26944458054
VL - 406
SP - 50
EP - 56
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
IS - 1-2
ER -