Acta Metallurgica Sinica (金属学报) 2013/49:12 PP.1604-1610
The kinetics of precipitation in A1-0.6Mg-0.9Si-0.2Cu (mass fraction,%)alloy under different conditions was investigated饰differential scanning calorimetric analyses (DSC) and micro- hardness measurements. The results show that, an exothermic peak at about 100-150℃can be observed in the DSC curve for the nature aged (T4) alloy, but no peak for the pre-aged (T4P) alloy, and the peak corresponding with β"phase moves toward the low temperature zone for T4P alloy. The fraction of transformation Y, the rate of transformation dY/dT, and the kinetic parameters such as activation energy Q and frequency factor k0 for GP zones dissolution and β" phase transformation were calculated by Avrami-Johnson-Mehl equation. The values of activation energy for GP zones dissolution after natural aging and pre-aging were 66 and 119 kJ/mol, respectively, and the values for β"phase formation after natural aging and pre-aging were 114 and 60 kJ/mol, respectively. The kinetics expressions were obtained as follows, for T4 alloy:YGP=1-exp [-1.3 x 107texp(-7977/T)], Yβ"=1-exp [-4.7 x l022t2exp(-27484/T)]; for T4P alloy:YAP=1-exp(-2.4 x1013texp(-14345/T)],Yp-1-exp[-2.9 x1011lt2exp(一14392/T)]. In addition, with the increasing of aging time, the whole trend of hardness changing for pre-aged alloy is increasing at first, and then keeps constant basically, but for the nature aged alloy, the hardness decreases after aging at 185℃for 20 min, which was explained by the kinetics obtained above.
 Miller W S, Zhuang L, Bottema J, Wittebrood A J, De Smet P, Haszler A, Vieregge A. Mater Sci Eng, 2000:A280:37.
 Birol Y, Karlik M. Scr Mater, 2006:55:625.
 Birol Y. Mater Sci Eng, 2005:A391:175.
 Liu H, Chen Y, Zhao G, Liu C M, Zuo L. Trnns Nonferrous Met Soc China, 2006:16:917.
 Zhen L, Kang S B. Scr Mater, 1997:36:1089.
 Ou B L, Shen C H. Scand J Metall, 2005:34:318.
 Esmaeili S, Lloyd D J. Acta Mater, 2005:53:5257.
 Wei F, Li J S, Chen C Q. Rare Met Mater Eng, 2008:37:1348(魏芳,李金山,陈昌麒.稀有金属材料与工程,2008:37:1348)
 Gupta A K, Jena A K, Chaturvedi M C. Scr Metall, 1988:22:369.
 Ghosh K S, Gao N. Traps Nonferrous Met Soc China,2011:21:1199.
 Oguocha I N A, Yannacopoulos S. Mater Sci Eng, 1997:A231:25.
 Edwards G A, Stiller K, Dunlop G L, Couper M J. Acta Mater, 1998:46:3893.
 De Geuser F, Lefebvre W, Blavette D. Philos Mag Gett, 2006:86:227
 Zhen L, Kang S B, Kim H W. Mater Sci Technol, 1997:13:905.
 Murayama M, Hono K. Acta Mater, 1999:47:1537.
 Miao W F, Laughlin D E. Metall Mater Traps, 2000:31A:361.
 Esmaeili S, Lloyd D J. Mater Chnract, 2005:55:307.
 An Y G, Zhang L, Vegter H, Hurkmans A. Metall Mater Traps, 2002:33A:3121.
 Luo A, Lloyd D J, Gupta A, Youdelis W V. Acta Metall Mater, 1993:41:769.
 Ortega A. Thermochim Acta, 1996:284:379.
 Matsuda K, Naoi T, Fhjii K, Uetani Y, Sato T, Kamio A,Ikeno S. Mater Sci Eng, 1999:A262:232.
 Chakrabarti D 3, Laughlin D E. Prog Mater Sci, 2004:49:389.
 Gaber A, Ali A M, Matsuda K, Kawabata T, Yamazaki T, Ikeno S. J Alloys Compd, 2007:432:149.
 Cuniberti A, Tolley A, Riglos M V, Giovachini R. Mater Sci Eng, 2010:A527:5307.
 Buha J, Lumley R N, Crosky A G, Hono K. Acta Mater,2007:55:3015.
 Galwey A K, Brown M E. Handbook of Thermal Analysis and Cadorimetry. Amsterdam:Elesvier, 1998:147