400oC. While, the hardness dramatically decreased as the annealing temperature increased to above 500oC. In former, the decrease of hardness is attributed to the decrease of dislocation density. In the latter, dramatic decrease in hardness results from the recrystallization and grain growth. Acknowledgements This project was financially supported by the National Natural Science Foundation of China (51071118, 51271136 and 50831004) the 973 Program of China (2010CB631003), and the 111 Project of China (B06025). References [1] Valiev RZ, Krasilnikov NA, Tsenev NK. Plastic deformation of alloys with submicron-grained structure. Mater Sci Eng A, 137 (1991) 35–40. [2] I. Sabirov, Y. Estrin, M.R. Barnett,et al. Enhanced tensile ductility of an ultra-fine-grained aluminum alloy. Scripta Materialia, 58 (2008) 163–166. [3] L. Jiang, M.T. Pe′rez-Prado, P.A. Gruber,et al. Texture, microstructure and mechanical properties of equiaxed ultrafine-grained Zr fabricated by accumulative roll bonding. Acta Materialia, 56 (2008) 1228–1242. [4] H.W. Ho¨ppel ,M. Kautz , C. Xu,et al. An overview: Fatigue behaviour of ultrafine-grained metals and alloys. International Journal of Fatigue, 28 (2006) 1001–1010. [5] A. Balyanov a, J. Kutnyakova a, N.A. Amirkhanova,et al. Corrosion resistance of ultrafine-grained Ti. Scripta Materialia, 51 (2004) 225–229. [6] Y.H. Zhao, Z. Horita, T.G. Langdon,et al. Evolution of defect structures during cold rolling of ultrafine-grained Cu and Cu–Zn alloys: Influence of stacking fault energy. Materials Science and Engineering A, 474 (2008) 342–347. [7] Honggang Jiang, Y. Theodore Zhu, Darryl P. Butt,et al. Microstructural evolution, microhardness and thermal stability of HPT-processed Cu. Materials Science and Engineering A, 290 (2000) 128–138. [8] Naoki Takata, Seong-Hee Lee, Nobuhiro Tsuji. Ultrafine grained copper alloy sheets having both high strength and high electric conductivity. Materials Letters, 63 (2009) 1757–1760. [9] Naoya Kamikawa, Nobuhiro Tsuji, Xiaoxu Huang,et al. Quantification of annealed microstructures in ARB processed aluminum. Acta Materialia, 54 (2006) 3055–3066. [10] Daisuke Terada, Seiya Inoue, Nobuhiro Tsuji. Microstructure and mechanical properties of commercial purity titanium severely deformed by ARB process. J Mater Sci 42 (2007) 1673–1681. [11] Majid Hoseini, Meysam Hamid Pourian, Florent Bridier, et al. Thermal stability and annealing behavior of ultrafine grained commercially pure titanium. Materials Science and Engineering A, 532 (2012) 58-63. [12] M.Ravi Shankar, Balkrishna C.Rao, Seongeyl, et al. Severe plastic deformation (SPD) of titanium at near-ambient temperature. Acta Materialia, 54 (2006) 3691-3700. [13] Xianfeng Jiang, Shunhua Xiang, Nailu Chen. Effect of annealing processes on recrystallization texture of cold rolling pure titanium strip. Material & Heat Treatment, 40 (2011) 18 (in Chinese).
RkJQdWJsaXNoZXIy MjM0NDE=