ICF13B

13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- of Ti-6Al 4V alloy without reduction in ductility. The most appropriate heat treatment was composed of STQ treatment at 1203 K for 60 s and short-time aging at 803 K for 40 s. Through this duplex heat treatment, the improvement rates of the tensile strength and fatigue strength reached 29 % and 22 %, respectively. Acknowledgements This work was supported by a Grant-in-Aid for Scientific Research (KAKENHI), No. 16560069 and No. 18560080. The authors gratefully acknowledge the generous support. References [1] T. Nishimoto, N. Nakanishi, J. Umeda, Mechanical Properties and Strengthening mechanism of pure Ti powder composite material reinforced with carbon nano particles, Transactions of JWRI, Vol. 40 (2011), No. 2, 66-68. [2] G. Lutjering and J. C. Williams, Titanium, Springer-Verlag, Berlin, 2003, p.7. [3] M. A. Imam and C. M. Gilmore, Fatigue and microstructural properties of quenched Ti-6Al-4V, Metallurgical Transaction A, Vol. 14A, pp. 233-240 (1983). [4] J. R. Kennedy, Fatigue behavior of solution-treated and quenched Ti-6Al-4V alloy, Materials Science and Engineering, Vol. 57, pp. 197-204 (1983). [5] T. Morita, W. Niwayama, K. Kawasaki and Y. Misaka, Strengthening of Ti-6Al-4V alloy by induction heat treatment, Transactions of the Japan Society of Mechanical Engineers (A), Vol. 64, No. 624, pp. 2115-2120 (1998). [6] T. Morita, K. Kawasaki and Y. Misaka, Short-time heat-treatment of Ti-6Al-4V α+β type titanium alloy, JP. 3762528 (2006). [7] T. Morita, K. Kawasaki and Y. Misaka, Short-time duplex heat-treatment of α+β type titanium alloy, JP. 3789852 (2006). [8] T. Morita, K. Hatsuoka, T. Iizuka and K. Kawakami, Strengthening of Ti-6Al-4V alloy by short-time duplex heat treatment, Materials Transaction, Vol. 46, No. 7, pp. 1681-1686 (2005). [9] K. Minakawa, Fatigue of titanium alloy, Tetu-to-hagane, Vol. 75, No. 7, pp. 1104-1111 (1989). [10]G. Sridhar, R. Gopalan and D. S. Sarma, A microstructural characterization of solution-treated titanium alloy Ti-6Al-4V, Metallography, Vol. 20, pp. 291-310 (1987).

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