Effects of Fe Addition on the Snoek-Type Damping Behavior of Surface-Oxidation-Treated Ti-Mo Alloys
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SNOEK relaxation, i.e., the anelastic relaxation caused by interstitial solute atoms in body-centeredcubic (bcc) metals, has been widely investigated in many bcc metals, such as Fe, Nb, Ta, and V.[1,2] The Snoek relaxation in substitutional alloys is often modified by the interaction between substitutional solutes and interstitial solutes in alloys, and this type of relaxation is usually called Snoek-type relaxation.[3] Recently, Yin et al.[4,5] applied the Snoek-type relaxation mechanism to the Ti-Nb alloys containing a high concentration of oxygen, in order to design a new type of high damping alloys with both the high strength and high damping capacity. Ti-Mo alloys and Ti-Nb alloys share some common mechanical properties with b Ti alloys, such as high strength, low modulus, suitable ductility, and superior workability for engineering application. Compared with Nb, Mo is a more effective b-phase stabilizing element for Ti alloys, because the equivalent Mo content efficient to suppress the bfi a¢¢ martensitic transformation to a temperature below room temperature is Moeq (mass pct) = 1.0Mo + 0.28Nb + 2.9Fe + …[6] HUI LU, Doctoral Student, Exploratory Materials Research Laboratory for Reliability and Safety, National Institute for Materials Science, Tsukuba, 305-0047, Japan, and Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei, 230031, P.R. China. Contact e-mail: [email protected] CHUNXIA LI, Doctoral Student, and OSAMU UMEZAWA, Professor, are with the Faculty of Engineering, Yokohama National University, Yokohama, 240-8501, Japan. FUXING YIN, Chief Researcher, is with the Exploratory Materials Research Laboratory for Reliability and Safety, National Institute for Materials Science. QIANFENG FANG, Professor, is with the Key Laboratory of Materials Physics, Institute of Solid State Physics. Manuscript submitted August 23, 2010. Article published online February 1, 2011 2242—VOLUME 42A, AUGUST 2011
On the other hand, previous internal friction studies on Nb-Mo-O[7–9] and Nb-Ti-O[7] indicate that Mo-O interaction and Nb-O interaction show different influences on the Snoek-type relaxations in b Ti alloys. It was also confirmed that substitutional solutes of Mo show a beneficial effect on the relative index of relaxation strength of O (relaxation strength at unit oxygen concentration) in the Nb-based alloys. According to the damping behavior of the designed Ti-Nb-O alloys,[5] lower b-phase stabilizing element content and lower oxygen content (higher relaxation strength at unit oxygen content) are required in order to make b Ti alloys with oxygen dissolved into advanced high damping alloys. The Ti-Mo-O alloy should be a perspective candidate considering these two conditions. The Fe is another effective b Ti stabilizer, considering the equivalent Mo content mentioned previously. Moreover, its strengthening potential,[10] low cost, and possible better damping properties compared to other b stabilizers suggest a potential substitutional solute. In general, the presence of substitutional solutes m
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