Deformation Mechanism and Hot Workability of Extruded Magnesium Alloy AZ31

doi:10.1007/s40195-017-0681-5

Abstract

Abstract:

Using the flow stress curves obtained by Gleeble thermo-mechanical testing, the processing map of extruded magnesium alloy AZ31 was established to analyze the hot workability. Stress exponent and activation energy were calculated to characterize the deformation mechanism. Then, the effects of hot deformation parameters on deformation mechanism, microstructure evolution and hot workability of AZ31 alloy were discussed. With increasing deformation temperature, the operation of non-basal slip systems and full development of dynamic recrystallization (DRX) contribute to effective improvement in hot workability of AZ31 alloy. The influences of strain rate and strain are complex. When temperature exceeds 350 °C, the deformation mechanism is slightly dependent of the strain rate or strain. The dominant mechanism is dislocation cross-slip, which favors DRX nucleation and grain growth and thus leads to good plasticity. At low temperature (below 350 °C), the deformation mechanism is sensitive to strain and strain rate. Both the dominant deformation mechanism and inadequate development of DRX deteriorate the ductility of AZ31 alloy. The flow instability mainly occurs in the vicinity of 250 °C and 1 s^-1.

Key words: Hot workability, Deformation mechanism, Dynamic recrystallization, Activation energy, Magnesium alloy

Zhao-Yang Jin, Nan-Nan Li, Kai Yan, Jian Wang, Jing Bai, Hongbiao Dong. Deformation Mechanism and Hot Workability of Extruded Magnesium Alloy AZ31[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(1): 71-81.

Figures/Tables 12

Fig. 1 OM a and SEM b morphologies of extruded AZ31 magnesium alloy

Fig. 2 True stress-strain curves of AZ31 magnesium alloy at 250 °C a, 400 °C b

Fig. 3 Processing maps of AZ31 alloy at strains of 0.2 a, 0.4 b

Fig. 4 Determination of n and Q at strain of 0.8: a $\ln \dot{\varepsilon } - \ln \left[ {\sinh \left( {\alpha \sigma } \right)} \right]$; bln [ sinh (ασ)] - 1/T $n\left( T \right) = 0.01241T - 1.71274.$ (13)

Fig. 5 Relationship plots of n-T a, Q/(nR) - ln $\dot{\varepsilon }$ b at strain of 0.8

Fig. 6 Relationship between deformation activation energy, temperature and strain rate at strain of 0.8

Fig. 7 3D a, 2D b maps of variation of n with T and ε

Fig. 8 Variation of Q with T, ε and $\dot{\varepsilon }$: a Q at strain rates of 0.001, 0.01 and 0.1 s-1; b Q at temperatures of 300, 350 and 400 °C

Fig. 9 OM a, c, SEM b, d images of AZ31 alloy deformed at 250 °C, 0.001 s-1 a, b, 400 °C, 0.001 s-1 c, d

Fig. 10 OM a, SEM b images of AZ31 alloy deformed at 250 °C, 1 s-1 at strain of 0.8

Fig. 11 Microstructure of AZ31 alloy deformed at 250 °C, 1 s-1 at strain of 0.2

Fig. 12 Variation of Q, n a, η b with true strain

References

[1]	K. Liu, X.H. Dong, H.Y. Xie, F. Peng, Mater. Sci. Eng., A 623, 97 (2015)
[2]	S. Housh, B. Mikucki, A. Stevenson, Selection and application of magnesium and magnesium alloys, 10th edn. (ASM International, Materials Park, OH, 1990), p. 455
[3]	W.L. Cheng, Q.W. Tian, H. Yu, B.S. You, H.X. Wang, Mater. Des. 85, 762(2015)
[4]	W.L. Cheng, Z.P. Que, J.S. Zhang, C.X. Xu, W. Liang, B.S. You, S.S. Park, Int. J. Miner. Metall. Mater. 20, 49(2013)
[5]	K.R. Athul, U.T.S. Pillai, A. Srinivasan, B.C. Pai, Adv. Eng. Mater. 18, 770(2016)
[6]	P. Zhou, Q.X. Ma, Acta Metall. Sin. (Engl. Lett.) 30, 907(2017)
[7]	J. Han, J.P. Sun, Y. Han, H. Liu, Acta Metall. Sin. (Engl. Lett.) 30, 1080(2017)
[8]	G.Z. Quan, H.R. Wen, J. Pan, Z.Y. Zou, Int. J. Precis. Eng. Manuf. 17, 171(2016)
[9]	Y.Y. Dong, C.S. Zhang, G.Q. Zhao, Y.J. Guan, A.J. Gao, W.C. Sun, Mater. Des. 92, 983(2016)
[10]	Y. Zhang, H.L. Sun, A.A. Volinsky, B.H. Tian, Z. Chai, P. Liu, Y. Liu, Acta Metall. Sin. (Engl. Lett.) 29, 422(2016)
[11]	C. Poletti, H. Dieringa, F. Warchomicka, Mater. Sci. Eng., A 516, 138 (2009)
[12]	Y.V.R.K. Prasad, K.P. Rao, Mater. Des. 30, 3723(2009)
[13]	Y.V.R.K. Prasad, K.P. Rao, Mater. Sci. Eng., A 487, 316 (2008)
[14]	N. Srinivasan, Y.V.R.K. Prasad, P.R. Rao, Mater. Sci. Eng., A 476(1-2), 146 (2008)
[15]	W.P. Peng, P.J. Li, P. Zeng, L.P. Lei, Mater. Sci. Eng., A 494(1-2), 173 (2008)
[16]	Y.C. Lin, F.Q. Nong, X.M. Chen, D.D. Chen, M.S. Chen, Vacuum 137, 104 (2017)
[17]	G.A. He, L.M. Tan, F. Liu, L. Huang, Z.W. Huang, L. Jiang, Materials 10, 161 (2017)
[18]	Y.V.R.K. Prasad, H.L. Gegel, S.M. Doraivelu, J.C. Malas, J.T. Morgan, K.A. Lark, D.R. Barker, Metall. Trans. A 15, 1883 (1984)
[19]	Z.Y. Jin, N.N. Li, K. Yan, J.X. Chen, D.L. Wei, Z.S. Cui, Acta Metall. Sin. (Engl. Lett.) (2017).
[20]	P. Dadras, J.F. Thomas, Metall. Trans. A 12, 1867 (1981)
[21]	S.V.S.N. Murty, M.S. Sarma, B.N. Rao, Metall. Mater. Trans. A 28, 1581 (1997)
[22]	S.V.S.N. Murty, B.N. Rao, B.P. Kashyap, Mater. Process. Technol. 166, 279(2005)
[23]	Y.V.R.K. Prasad, K.P. Rao, S. Sasidhara, Hot working guide: a compendium of processing maps, 2nd edn. (ASM International, Materials Park, OH, 2015), p. 13
[24]	C.M. Sellars, W.J.M. Tegart, Int. Metall. Rev. 17, 1(1972)
[25]	D.G. He, Y.C. Lin, M.S. Chen, J. Chen, D.X. Wen, X.M. Chen, J. Alloys Compd. 649, 1075(2015)
[26]	Y.P. Li, R.B. Song, E.D. Wen, F.Q. Yang, Acta Metall. Sin. (Engl. Lett.) 29, 441(2016)
[27]	H.J. Frost, M.F. Ashby, Deformation mechanism maps: the plasticity and creep of metals and ceramics (Pergamon Press, Oxford, 1982), p. 44
[28]	R. Gehrmann, M.M. Frommert, G. Gottstein, Mater. Sci. Eng., A 395, 338 (2005)
[29]	H. Yoshinaga, R. Horiuchi, Trans. Jpn. Inst. Metals 5, 14 (1964)
[30]	P.W. Flynn, J. Mote, J.E. Dorn, Trans. Metall. Soc. AIME 221, 1148 (1961)
[31]	Y.V.R.K. Prasad, K.P. Rao, Mater. Sci. Eng., A 432, 170 (2006)
[32]	T. Obara, H. Yoshinga, S. Morozumi, Acta Metall. 21, 845(1973)
[33]	Z. Feng, X. Zhang, F. Pan, Rare Metal. Mater. Eng. 41, 1765(2012)
[34]	D.H. Sastry, Y.V.R.K. Prasad, K.I. Vasu, Scr. Metall. 3, 927(1969)
[35]	M.H. Yoo, S.R. Agnew, J.R. Morris, K.M. Ho, A 319, 87 (2001)
[36]	D.X. Wen, Y.C. Lin, Y. Zhou, Vacuum 141, 316 (2017)
[37]	Z.Y. Jin, D.H. Yu, X.T. Wu, K. Yin, K. Yan, J. Mater. Sci. Technol. 32, 1260(2016)
[38]	J.R. Morris, J. Scharff, K.M. Ho, D.E. Turner, Y.Y. Ye, M.H. Yoo, Philos. Mag. A 76, 1065 (1997)
[39]	J. Koike, T. Kobayashi, T. Mukai, H. Watanabe, M. Suzuki, K. Maruyama, K. Higashi, Acta Mater. 51, 2055 (2003)
[40]	D.D. Chen, Y.C. Lin, Y. Zhou, M.S. Chen, D.X. Wen, J. Alloys Compd. 708, 938(2017)
[41]	Z.H. Zhou, Q.C. Fan, Z.H. Xia, A.G. Hao, W.H. Yang, W. Ji, H.Q. Cai, J. Mater. Sci. Technol. 33, 637(2017)
[42]	F. Berge, L. Krüger, H. Ouaziz, C. Ullrich, Trans. Nonferrous Met. Soc. China 25, 1 (2015)
[43]	D.X. Wen, Y.C. Lin, J. Chen, J. Deng, X.M. Chen, J.L. Zhang, M. He, Mater. Sci. Eng., A 620, 319 (2015)
[44]	J. Koike, Mater. Sci. Forum 419, 189 (2003)
[45]	J. Koike, R. Ohyama, T. Kobayashi, M. Suzuki, K. Maruyama, Mater. Trans. 44, 445(2005)
[46]	H.Y. Wu, C.T. Wu, J.C. Yang, M.J. Lin, Mater. Sci. Eng., A 607, 261 (2014)