Characterization of the β Phase Decomposition in Ti-5Al-5Mo-5V-3Cr at Slow Heating Rates

Quentin Contrepois, Marc Carton, Jacqueline Lecomte-Beckers

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DOI: 10.4236/ojmetal.2011.11001                

Abstract

The influence of slow heating rates: 2, 5, 10 and 30?C/min (0.033, 0.083, 0.166 and 0.50℃/s) on the β phase decomposition of Ti-5Al-5Mo-5V-3Cr (Ti-5553) during continuous heating were characterized by differential scanning calorimetry (DSC) analysis, light microscopy, scanning electron microscopy, X-ray diffraction and hardness testing. Starting microstructure was the β phase obtained by heating the Ti-5553 above the Tβ temperature and a water quench. Results show that heating rate has a significant impact on the precipitation mechanisms and on the β→α transformation in this range of heating rates. The main formation of α precipitates occurs between 500 and 600℃at all heating rates tested.A heating at 2℃/min produces very fine and homogeneously distributed α plate precipitates which have nucleated on the nanometer size ωiso precipitates. The ω_iso precipitates between 350 and 400℃. At higher heating rates 10, 15 or 30℃/min, the amount of precipitation of ω_iso is lower so an additional formation of nanometer size precipitates occurs between 450 and 500℃ It is supposed that both precipitates act as nucleation sites for α phase precipitation. The resultant microstructure consists in a fine intragranular distribution of α precipitates and a coarser precipitation of α at the grain boundaries. It is shown that the precipitation of ω_iso phase retards or prevents the precipitation of nanometer size precipitates occurring between 450 and 500℃. This cannot be generalized to all the β-metastable titanium alloys since Ti-LCB does not exhibit the same heating rate dependence on DSC curves.

Keywords

β Metastable Titanium Alloy, ω Phase, Precipitation, Microstructure, DSC

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	N. G. Jones, R. J. Dashwood, D. Dye and M. Jackson, “Ther-momechanical Processing of Ti-5Al-5Mo-5V-3Cr,” Material Sciences and Engineering: A, Vol. 490, 2008, pp. 369-377. doi:10.1016/j.msea.2008.01.055
[2]	I. Weiss and S. L. Semiatin, “Thermomechanical Processing of Beta Titanium Alloys: An Overview,” Material Sciences and Engineering: A, Vol. 243, 1998, pp. 46-65. doi:10.1016/S0921-5093(97)00783-1
[3]	G. Lütjering, “In-fluence of Processing on Microstructure and Mechanical Prop-erties of (α+β) Titanium Alloys,” Material Sciences and Engi-neering: A, Vol. 243, 1998, pp. 32-45. doi:10.1016/S0921-5093(97)00778-8
[4]	O. M. Ivasishin, P. E. Markovsky, S. L. Semiatin and C. H. Ward, “Aging Re-sponse of Coarse- and Fine-Grained β Titanium Alloys,” Mate-rial Sciences and Engineering: A, Vol. 405, 2005, pp. 196-305. doi:10.1016/j.msea.2005.06.027
[5]	O. M. Ivasishin, P. E. Markovsky, Yu. V. Matviychuk, S. L. Semiatin, C. H. Ward and S. Fox, “A Comparative Study of the Mechanical Proper-ties of High-Strength β-Titanium Alloys,” Journal of Alloys and Compounds, Vol. 457, 2008, pp. 296-309. doi:10.1016/j.jallcom.2007.03.070
[6]	N. Wain, X. J. Hao, G. A. Ravi and X. Wu, “The Influence of Carbon on Precipitation of α in Ti-5Al-5Mo- 5V-3Cr,” Material Sciences and Engi-neering: A, Vol. 527, 2010, pp. 7673-7683. doi:10.1016/j.msea.2010.08.032
[7]	H. Chang, E. Aeby-Gautier, F. Bruneseaux and L. Zhou, “The Influence of Heating Rate on Phase Transformation Kinetics and Micro-structures Evolutions at Ageing in MeTastable β Titanium Al-loy Ti-B19,” In: M. Nimoni, S. Akiyama, M. Ikeda, M. Hagi-wara, K. Maruyama, Eds., Ti-2007 Science And Technology, The Japan Institute, Vol. 2, 2007, pp. 973-976.
[8]	F. Brune-seaux, G. Geandier, E. Gauthier, B. Appolaire, M. Dehmas and P. Boulet, “In Situ Characterization of the Transformation Se-quences of Ti17 Alloy by High Energy X-ray Diffraction: In-fkuence of the Thermal Path,” In: M. Nimoni, S. Akiyama, M. Ikeda, M. Hagiwara, K. Maruyama, Eds., Ti-2007 Science and Technology, The Japan Institute, Vol. 1, 2007, pp. 563-566.
[9]	Y. Ohmori, T. Ogo, K. Nakai, S. Kobayashi, “Effects of ω-phase Precipitation on β-->α, α'' Transformations in a Metastable β Titanium Alloy,” Material Sciences and En-gineering: A, Vol. 312, 2001, pp. 182-188. doi:10.1016/S0921-5093(00)01891-8
[10]	F. Prima, P. Ver-naut, G. Texier, D. Ansel and T. Gloriant, “Evidence of Α-nanophase Heterogeneous Nucleation from Ω Particles in a β-metastable Ti-based Alloy by High-Resolution Electron Mi-croscopy,” Scripta Materialia, Vol. 54, 2006, pp. 645-648. doi:10.1016/j.scriptamat.2005.10.024
[11]	N. G. Jones, R. J. Dashwood, D. Dye and M. Jackson, “Development of Chev-ron-shaped α Precipitates in Ti- 5Al- 5Mo-5V-3Cr,” Scripta Materialia, Vol. 60, 2009, pp. 571-573. doi:10.1016/j.scripta-mat.2008.12.010
[12]	S. Nag, R. Banerjee, R. Srinivasan, J. Y. Hwang, M. Harper and H. L. Fraser, “ω-Assisted Nucleation and Growth of α Precipitates in the Ti-5Al-5Mo-5V-3Cr-0.5Fe β Titanium Alloy,” Acta Materialia, Vol. 57, 2009, pp. 2136- 2147. doi:10.1016/j.actamat.2009.01.007
[13]	N. G. Jones, R. J. Dashwood, M. Jackson and D. Dye, “β-Phase Decomposition in Ti-5Al-5Mo-5V-3Cr,” Acta Materialia, Vol. 57, 2009, pp. 3830-3889. doi:10.1016/j.actamat.2009.04.031
[14]	S. Azimzadeh and H. J. Rack, “Phase Transformations in Ti-6.8Mo-4.5Fe-1.5Al,” Metallurgical Transaction: A, Vol. 29, 1998, pp. 2455-2467. doi:10.1007/s11661-998-0217-8
[15]	F. Prima, “Etude Métal-lurgique D’un Nouvel Alliage de Titane β-métastable,” PhD Thesis, INSA Rennes, France, 2000.
[16]	M. Carton, P. Jacques, N. Clément and J. Lecomte-Beckers, “Study of Transformations and Microstructural Modifications in Ti-LCB and Ti-555 Al-loys Using Differential Scanning Calorimetry,” In: M. Nimoni, S. Akiyama, M. Ikeda, M. Hagiwara, K. Maruyama, Eds., Ti-2007 Science and Technology, The Japan Institute, Vol. 1, 2007, pp. 491-494.
[17]	A. Dehghan-Manshadi and R. J. Dip-penaar, “Development of α-Phase Morphologies During Low Temperature Isothermal Heat Treatment of a Ti-5Al-5Mo-5V-3Cr Alloy,” Material Sciences and Engineering: A, Vol. 528, 2011, pp. 1833-1839. doi:10.1016/j.msea.2010.09.061
[18]	N. Clément, “Phase Transformations and Mechanical Properties of the Ti-5553 β-metastable Titanium Alloy,” PhD Thesis, UCL, Belgium, 2010.