Through Thickness Microstructural Gradients in 7475 and 2022 Creep - Ageformed Bend Coupons

Bakavos, D.; Prangnell, P.B.; Bes, Bernard; Eberl, Frank; Gardiner, S.

doi:10.4028/www.scientific.net/msf.519-521.407

Cited by 16 publications

(10 citation statements)

References 10 publications

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“…(b) Yield strength in slightly over-aged conditions without (conventionally aged) and with an applied tensile stress of 50 MPa (stress-aged) [11]. (c) Mean particle radius of Z 0 precipitation in AA7475 [25].…”

Section: Materials Modellingmentioning

confidence: 99%

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A review of the development of creep age forming: Experimentation, modelling and applications

Zhan

Lin

Dean

2011

International Journal of Machine Tools and Manufacture

228

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Section: Materials Modellingmentioning

confidence: 99%

“…Bakavos et al [14,25] carried out experimental research, using industrial scale age forming tools, to evaluate through thickness microstructure variation for AA7475 and AA2022. Plates with 20 mm thickness of the two alloys were age formed on a single curvature tool with a radius of 3180 mm.…”

Section: Stress/strain Age (Precipitation) Hardeningmentioning

confidence: 99%

A review of the development of creep age forming: Experimentation, modelling and applications

Zhan

Lin

Dean

2011

International Journal of Machine Tools and Manufacture

228

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“…To date, although the phenomenon of asymmetric stress relaxation had been observed in industrial CAF, the underlying mechanism remains unclear. Bakavos et al (2006) studied the through-thickness microstructural gradients in 7475 and 2022 post-CAF coupons. In their investigation, 20-mm-thick plates were creep-age formed at a 3180 mm single radius curvature tool using an autoclave and vacuum bagging system.…”

Section: Asymmetric Through-thickness Stress Relaxationmentioning

confidence: 99%

Influences of residual stresses and initial distortion on springback prediction of 7B04-T651 aluminium plates in creep-age forming

Lam

Shi

Lin

et al. 2015

International Journal of Mechanical Sciences

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Abstract. Springback behaviour of surface-machined 7B04-T651 aluminium plates of 3 to 8 mm thicknesses, creep-age formed under a single curvature bending radius of 1200 mm, has been experimentally investigated. The surface residual stress levels of the plates have been measured and the typical residual stress distribution and values in 7000-series aluminium alloys have been reviewed and analysed. Finite element models have been developed to simulate creep-age forming (CAF) processes and predict the amount of springback in the physical CAF test. Machining-induced residual stresses and distortion have been considered in the finite element models. This paper presents a first attempt to study the effect of machining-induced residual stresses on the errors of springback prediction in CAF of 7000-series aluminium alloy panel components. It has been found that the effect of machininginduced residual stresses on the accuracy of springback prediction is related to the initial loading stress levels in CAF. In addition, when the initial distortion conforms to the loading curvature, an opposing effect on the material's deformation is observed. Creep-ageing material constant related to effective creep strain rate.1 Creep-ageing material constant related to rate of age hardening.2 Creep-ageing material constant related to the depletion of solute into precipitate.3 Creep-ageing material constant related to rate of precipitate growth.4 Creep-ageing material constant controlling the effect of dislocation density (or creep) on precipitate nucleation and growth.5 Creep-ageing material constant related to rate of dislocation density.Creep-ageing material constant related to rate of dislocation hardening.Bending radius of forming tool.̅ , ̅ Normalised precipitate size and its rate term respectively. ̅ 0 Initial value for normalised precipitate size.Radius of revolvement of workheads of the flexible form tool.Creep-ageing time.1 , 2 , 3 , 4 Time of loading, heating, cooling and unloading respectively. Artificial ageing time.Solution heat treatment time., , Translational degrees of freedom in Cartesian coordinates., , Rotational degrees of freedom in Cartesian coordinates.Poisson's ratio., , Cartesian coordinates., positions of the lower and upper splines respectively.

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“…Spring back after CAF was calculated using Equation 12. Coupons with thickness of 10 mm presented spring back values around 68% while coupons with thickness of 15 mm presented spring back values around 60%.…”

Section: Creep Age Forming Testsmentioning

confidence: 99%

Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

2014

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CAF process combines creep and precipitation hardening which are highly dependent on time and temperature. The aging cycle relax the stresses induced during the loading phase. At the end of the process stress relaxation induces shape changes in the part but significant spring back is observed (about 70%). Usually CAF cycles for 7XXX alloys use times around 20 h and temperatures in the range of 120°C to 190°C. In the present work CAF tests were performed using the alloy 7050 in an intermediate condition named Temper to Age Forming (TAF). Using the alloy 7050-TAF resulted in significant process time reduction. From TAF temper, only 8 hours are necessary to achieve properties comparable to T74. Coupons were submitted to CAF in two levels of initial stress, 190 MPa and 290 MPa, resulting in spring back values of 70% and 60 % respectively. In addition, constant load creep tests were performed in the same stress levels and time of CAF tests to find the creep strain values. Creep tests performed under 190 MPa resulted in strain values around 0,1% after 8 h. On the other hand creep tests performed under 290 MPa failed after 7 h with creep strain values of 1,7%. Results obtained are close to that found in previous studies and it is possible to conclude that the use of alloy 7050 in TAF condition allows CAF to be done in 8 hours, since the initial stress is lower than 290 MPa.

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Through Thickness Microstructural Gradients in 7475 and 2022 Creep - Ageformed Bend Coupons

Cited by 16 publications

References 10 publications

A review of the development of creep age forming: Experimentation, modelling and applications

A review of the development of creep age forming: Experimentation, modelling and applications

Influences of residual stresses and initial distortion on springback prediction of 7B04-T651 aluminium plates in creep-age forming

Evaluation of a 7050-TAF aluminum alloy submitted to creep age forming

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