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Phase equilibria and phase transformation of the body-centered cubic phase in the Cu-rich portion of the Cu–Ti–Al system

Published online by Cambridge University Press:  31 January 2011

X.J. Liu*
Affiliation:
Department of Materials Science and Engineering, College of Materials, and Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005, People’s Republic of China
C.P. Wang
Affiliation:
Department of Materials Science and Engineering, College of Materials, and Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005, People’s Republic of China
I. Ohnuma
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
R. Kainuma
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
K. Ishida
Affiliation:
Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

The phase equilibria and phase transformation of the body-centered cubic (bcc) phase in the Cu–Ti–Al system were investigated by the diffusion couple method, metallographic examination, differential scanning calorimetry, and x-ray diffraction. The isothermal sections at 700 and 900 °C and vertical sections at 18 at.% Al, 22 at.% Al, and 25 at.% Al in the Cu-rich portion were determined. These results indicate that (i) the Cu2TiAl compound with the L21 Heusler structure has a larger solubility range; (ii) the stable B2 + L21 miscibility gap of the ordered bcc phase exists until the liquid phase, and the tie lines of this miscibility gap are almost parallel with the Cu–Ti side; (iii) the composition and temperature for the eutectic reaction (L ↔ B2 + L21) are about 7 at.% Ti and about 970 °C, respectively, and (iv) the velocity of the eutectoid decomposition [bcc ↔ face-centered cubic (fcc) + D83] of the bcc phase with martensitic morphology in the Cu–Ti–Al alloys is slower than that of the Cu–Al alloys.

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Copyright
Copyright © Materials Research Society 2008

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References

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