In the present paper, the effect of stress on precipitation behaviour, which decides the strength of 7xxx alloy, has been investigated through a comparative analysis of the difference in precipitation behaviour in 7050 alloy treated by age forming and traditional aging. The results suggest that the stress can enhance precipitate nucleation and growth in age forming, which mainly attributes to two reasons. First, the increased diffusion coefficient caused by applied stress field in age forming induces precipitates to growth. Second, in age forming, obvious dislocation movement caused by initial stress supplied short circuit diffusion passway and nucleation interface is of benefit to the precipitate nucleation and growth. Besides, the promoting precipitation effect decays gradually with stress relaxation during the age forming process.
ZhanL., LinJ. and DeanT. A.: ‘A review of the development of creep age forming: experimentation, modelling and applications’, Int. J. Mach. Tools Manuf., 2011, 51, 1–17. doi: 10.1016/j.ijmachtools.2010.08.007
2.
IdemK. and PeddiesonJ.: ‘Simulation of the age forming process’, J. Manuf. Sci. Eng., 2005, 127, 165–172. doi: 10.1115/1.1828058
3.
StarinkM. J., GaoN., KampN., WangS. C., PitcherP. D. and SinclairI.: ‘Relations between microstructure, precipitation, age-formability and damage tolerance of Al-Cu-Mg-Li (Mn, Zr, Sc) alloys for age forming’, Mater. Sci. Eng. A, 2006, A418, 241–249. doi: 10.1016/j.msea.2005.11.023
4.
HoK. C., LinJ. and DeanT. A.: ‘Modelling of springback in creep forming thick aluminum sheets’, Int. J. Plast., 2004, 20, 733–751. doi: 10.1016/S0749-6419(03)00078-0
5.
SallahM., PeddiesonJ. and ForoudastanS.: ‘A mathematical model of autoclave age forming’, J. Mater. Process. Technol., 1991, 28, 211–219. doi: 10.1016/0924-0136(91)90220-9
6.
SkrotzkiB., ShifletG. and StarkeE.: ‘On the effect of stress on nucleation and growth of precipitates in an Al-Cu-Mg-Ag alloy’, Metall. Mater. Trans. A, 1996, 27A, 3431–3444. doi: 10.1007/BF02595436
7.
ZhuA. and StarkeE.: ‘Stress aging of Al-xCu alloys: experiments’, Acta Mater., 2001, 49, 2285–2295. doi: 10.1016/S1359-6454(01)00119-7
8.
ZhuA. and StarkeE.: ‘Materials aspects of age-forming of Al-xCu alloys’, J. Mater. Process. Technol., 2001, 117, 354–358. doi: 10.1016/S0924-0136(01)00795-6
9.
ZhuA. and StarkeE.: ‘Stress aging of Al-Cu alloys: computer modeling’, Acta Mater., 2001, 49, 3063–3069. doi: 10.1016/S1359-6454(01)00202-6
10.
LiD. and ChenL. Q.: ‘Computer simulation of stress-oriented nucleation and growth of θ′ precipitates in Al-Cu alloys’, Acta Mater., 1998, 46, 2573–2585. doi: 10.1016/S1359-6454(97)00478-3
11.
EtoT., SatoA. and MoriT.: ‘Stress-oriented precipitation of G.P. zones and θ′ in an Al-Cu alloy’, Acta Metall., 1978, 26, 499–508. doi: 10.1016/0001-6160(78)90175-X
12.
HosfordW. and AgrawalS.: ‘Effect of stress during aging on the precipitation of θ′ in Al-4Cu’, Metall. Mater. Trans. A, 1975, 6A, 487–491. doi: 10.1007/BF02658406
13.
FanX. H., LiM., LiD. Y., ZhangS. R. and PengY. H.: ‘Dynamic recrystallisation and dynamic precipitation in AA6061 aluminium alloy during hot deformation’, Mater. Sci. Technol., 2014, 30, 1263–1272. doi: 10.1179/1743284714Y.0000000538
14.
KhanI., StarinkM. and YanJ. L.: ‘A model for precipitation kinetics and strengthening in Al-Cu-Mg alloys’, Mater. Sci. Eng. A, 2008, A472, 66–74. doi: 10.1016/j.msea.2007.03.033
15.
ChenJ. F., ZhenL., JiangJ. J., YangL., ShaoW. Z. and ZhanB. Y.: ‘Microstructures and mechanical properties of age-formed 7050 aluminum alloy’, Mater. Sci. Eng. A, 2012, A539, 115–123. doi: 10.1016/j.msea.2012.01.067
16.
JiangX., TaftoJ., NobleB., HolmeB. and WaterlooG.: ‘Differential scanning calorimetry and electron diffraction investigation on low-temperature aging in Al-Zn-Mg alloys’, Mater. Trans. A, 2000, 31A, 339–348. doi: 10.1007/s11661-000-0269-x
17.
GhoshK. S. and GaoN.: ‘Determination of kinetic parameters from calorimetric study of solid state reactions in 7150 Al-Zn-Mg alloy’, Trans. Nonferr. Met. Soc. China, 2011, 21, 1199–1209. doi: 10.1016/S1003-6326(11)60843-1
18.
ShaG. and CerezoA.: ‘Early-stage precipitation in Al-Zn-Mg-Cu alloy (7050)’, Acta Mater., 2004, 52, 4503–4516. doi: 10.1016/j.actamat.2004.06.025
19.
KongthepJ. and JuijermP.: ‘Kinetics of precipitation hardening phase in aluminium alloy AA 6110.Mater’, Sci. Technol., 2014, 30, 1815–1829.
20.
FlynnC. and StonehamA.: ‘Quantum theory of diffusion with application to light interstitials in metals’, Phys. Rev. B, 1970, 1B, 3966–3975. doi: 10.1103/PhysRevB.1.3966
21.
ArdellA. J. and PrikhodkoS. V.: ‘Coarsening of γ′ in Ni-Al alloys aged under uniaxial compression. II: diffusion under stress and retardation of coarsening kinetics’, Acta Mater., 2003, 51, 5013–5019. doi: 10.1016/S1359-6454(03)00327-6
RobeyR. F., PrangnellP. B. and DifR.: ‘A comparison of the stress relaxation behaviour of three aluminium aerospace alloys for use in age-forming applications’, Mater. Forum, 2004, 28, 132–138.
24.
DeschampsA., FribourgG., BréchetY., CheminJ. L. and HutchinsonC. R.: ‘In situ evaluation of dynamic precipitation during plastic straining of an Al-Zn-Mg-Cu alloy’, Acta Mater., 2012, 60, 1905–1916. doi: 10.1016/j.actamat.2012.01.002
25.
DeschampsA. and BrechetY.: ‘Influence of pre-deformation and ageing of an Al-Zn-Mg alloy-II. Modeling of precipitation kinetics and yield stress’, Acta Mater., 1998, 47, 293–305. doi: 10.1016/S1359-6454(98)00296-1
