Effect of Zr Addition on Phase Constitution and Heat Treatment Behavior of Ti-25mass%Nb Alloys

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In an attempt to optimize the shape recovery temperature, the effect of Zr addition on phase constitution and heat treatment behavior is investigated by electrical resistivity and Vickers hardness (HV) measurements, X-ray diffractometry (XRD) and shape recovery tests. Ti-25mass%Nb-0, 2, 7 and 12mass%Zr alloys (abbreviated as 0Zr, 2Zr, 7Zr and 12Zr, respectively) were prepared using an arc-furnace. Specimens were solution-treated at 1273 K for 3.6 ks and then quenched by iced water (STQ). STQed specimens were isochronally heat-treated. In 0Zr and 2Zr, only the orthorhombic martensite phase a” was identified by XRD, while the two-phase alloys a” and b were identified in 7Zr and 12Zr. In 7Zr, resistivity at liquid nitrogen and room temperature (rLN and rRT, respectively) and resistivity ratio (rLN/rRT) drastically increased at 523 K because of the reverse-transformation of a” into b phase. Thereafter, resistivity and resistivity ratio decreased with increasing heat treatment temperature due to isothermal w precipitation. Starting temperature of shape recovery is 623 K in 7Zr and 523 K in 12Zr. In 7Zr, shape recovery ratio is about 80% at 723 K, which is the maximum obtained in this study.

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Periodical:

Materials Science Forum (Volumes 475-479)

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Edited by:

Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie

Pages:

2337-2342

Citation:

M. Ikeda et al., "Effect of Zr Addition on Phase Constitution and Heat Treatment Behavior of Ti-25mass%Nb Alloys", Materials Science Forum, Vols. 475-479, pp. 2337-2342, 2005

Online since:

January 2005

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$38.00

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