Strain-Induced Grain Refinement in Magnesium Alloy AZ31 during Hot Forging

Abstract:

Strain-induced grain refinement in a magnesium alloy AZ31 was studied in multi-directional forging (MDF) at a temperature range from 423K to 623K and at a strain rate of 3x10-3s-1. MDF with a pass strain of 0.8 was carried out to high cumulative strains of around 5 with changing of the loading direction during decreasing temperature from pass to pass. The structural changes can be characterized by the evolution of many mutually crossing kink bands at low strains followed by increase in their number and misorientation, finally resulting in a fully developed fine-grains at high strains. MDF with decreasing temperature can accelerate the evolution of much finer grains and the improvement of plastic workability. An average grain size of 0.3 μm is formed at an accumulative strain of 4.8 and at 423K. It is concluded that grain refinement under MDF conditions occurs by a series of deformation-induced continuous reactions; that is essentially similar to continuous dynamic recrystallization (cDRX).

• Periodical: Materials Science Forum (Volumes 503-504)
• Pages: 521-526
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.503-504.521
• Online since: January 2006
• Authors: Xu Yue Yang, Jie Xing, Hiromi Miura, Taku Sakai
• Keywords: Continuous Dynamic Recrystallization, Fragmentation, Kink Bands, Magnesium Alloy, Multi-Directional Forging, Ultrafine Grained

References

[1] B.L. Mordike and T. Ebert: Materials Science and Engineering A Vol. 302 (2001), p.37.

[2] Y. Chino and M. Mabuchi: J. Jpn Inst of Light Metals. Vol. 51 (2001), p.498.

[3] H. Watanabe, T. Mukai and K. Higashi: J. Jan Inst of Light Metals Vol. 51 (2001), p.503.

[4] J. Xing, H. Soda, X. Yang, H. Miura and T. Sakai: J. Jpn Inst of Light Metals Vol. 54 (2004), p.527.

[5] S.E. Ion, F. J. Humphreys and S.H. White: Acta Metall. Vol. 30 (1982), p. (1909).

[6] A. Galiyev, R. Kaibyshev and G. Gottstein: Acta Mater. Vol. 49 (2001), p.1199.

[7] X. Yang, H. Miura and T. Sakai: Materials Science Forum Vol. 419-422 (2003), p.515, Vol. 426-432 (2003), p.611, Vol. 467-470 (2004), p.531.

[8] X. Yang, H. Miura and T. Sakai: Mater. Trans. Vol. 44 (2003), p.197.

[9] T. Sakai and J. J. Jonas: Encyclopedia of Materials: Science and Technology (Buschow et al., Eds., Elsevier, Oxford, 2001), p.7079.

[10] F.J. Humphreys and M. Hatherly: Recrystallization and Related Annealing Phenomena (Pergamon, 1995), p.21.

[11] O. Sitdikov, T. Sakai, A. Goloborodko, H. Miura, R. Kaibyshev: Mater. Trans. Vol. 45 (2004), p.2232.

[12] J. Koike, R. Ohyama, T. Kobayasi, M. Suzuki and K. Maruyama: Mater. Trans. Vol. 44 (2003), p.1.

[13] Y. Yoshida, L. Cisar, S. Kamado and Y. Kojima: J. Jpn Inst of Light Metals Vol. 53 (2002), p.559.