Stress-level-dependency and bimodal precipitation behaviors during creep ageing of Al-Cu alloy: Experiments and modeling

Ma, Zhi; Zhan, Lihua; Liu, Chunhui; Xu, Lingzhi; Xu, Yang; Ma, Peipei; Li, Jianjun

doi:10.1016/j.ijplas.2018.07.001

Cited by 109 publications

(24 citation statements)

References 57 publications

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“…This process, as a combination of two heating operations, involves the use of heat treatment at 973 K for only 0.5 h and low-temperature aging at 723 K for longer times. Such a strategy is typically used to strengthen the Al 2xxx series alloys, wherein dislocations interact with the so-called GP zones in the form of nanoscale inclusions [47][48][49][50][51].…”

Section: Introductionmentioning

confidence: 99%

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals

et al. 2020

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Fe 50 Ni 28 Co 17 Al 11.5 Ta 2.5 single crystals oriented along the [001] direction were investigated in order to establish the influence of two-step aging conditions on superelastic properties. The homogenized and quenched single crystalline material was subjected to a combination of high-temperature and low-temperature heat treatment at 973 K for 0.5 h and at 723 K for various aging times, respectively. As a result, fine and coherent γ' precipitates were formed. Using diffraction of high energy synchrotron radiation, the volume fraction of γ' precipitates was computed while their size was determined by high resolution TEM analysis. Compared with one-step heat treatment, the two-step aging process enables control of the precipitate size in a more accurate way. Moreover, it allows one to obtain a higher volume fraction of precipitates without increasing their size significantly. The obtained coherent γ' precipitates ranged in size from 5 to 8 nm; that considerably improved mechanical properties. The highest superelastic response was obtained for single crystals aged at 973 K for 0.5 h followed by aging at 723 K for 3 h. The single crystals treated with such conditions exhibited a superelastic strain of 15% in which the mechanical martensite stabilization was substantially suppressed.

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Section: Introductionmentioning

confidence: 99%

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals

et al. 2020

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“…A huge amount of dislocations is introduced in 240CA compared with SFA, resulting in a large amount of T1 precipitates in the grain interior. Dislocations in low‐stress aging and stress‐free aging are in a pretty small density and difficult to be measured . The nucleation and growth of T1 precipitates consume Cu and Li elements, and the development of δ ′ and θ ′ phases is constrained .…”

Section: Discussionmentioning

confidence: 99%

“…Al–Cu–Li alloys are broadly applied in manufacturing aircrafts and rockets because of their light weight and excellent properties, such as low density and high elastic modulus . A forming technology called creep age forming (CAF) has been applied to manufacture large integral component of aluminum alloys, like upper wing panel of Hawk aeroplane and wing skin for A380, during which shaping and strengthening of the material can be concurrently accomplished under external stress and at elevated temperature . Researchers have conducted many investigations on how CAF acts on novel aluminum alloys and aluminum–lithium alloys and they found that CAF can enhance the forming ability and stimulate growth of precipitates through regulating process parameters like time, temperature, applied stress, heating rate, and so on.…”

Section: Introductionmentioning

confidence: 99%

The effect of creep aging on localized corrosion resistance of AA2060 alloy

Wang

Zhan

Liu

et al. 2019

Materials & Corrosion

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The influence of creep aging at varied stresses on the localized corrosion behavior of AA2060 has been studied in this paper. Samples were subjected to stress free aging (SFA) and creep aging (CA) under two stress levels, after which tensile tests and intergranular corrosion (IGC) tests were carried out. The corrosion morphology and depth were examined using optical microscope. Compared with SFA, CA can enhance the mechanical properties and increase the IGC resistance of Al–Cu–Li alloy but high‐stress CA would intensify the intragranular corrosion penetration in the first 25 hr of aging time. The microstructure observation results show that dislocations introduced by CA provide favorable nucleation sites for T1 precipitates in the grain and impede the growth of T1 precipitates at grain boundary. Therefore, the potential difference between the grain interior and grain boundary can be reduced compared to that for the SFA. The mechanism by which CA affects the corrosion resistance of Al–Cu–Li alloys, as is essential to understand and optimize the creep aging process, has been proposed by considering the effect of creep‐deformation‐induced dislocations.

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“…Therefore, the yield strength in this state is slightly lower than initial state. Ma et al and Zheng et al [13,14] also demonstrated that the coarsening of the precipitates can be accelerated under higher stress. The comparison of Figure 6b,e shows that the average diameter of the η -precipitate after stress relaxation aging of 6% pre-strain is about 20 nm.…”

Section: Aging Behavior Of Aa7150 Under Different Temperatures Initimentioning

confidence: 96%

“…Subsequently, this macro-micro modeling method based on the hardening and softening mechanism was generalized. Zhang et al [12] and Ma et al [13] extended the equation to a wider stress and temperature range and characterized the microscopic factors (precipitate size, volume fraction and aspect ratio) in more detail. Zheng et al [14] established a deformation constitution model of the stress relaxation.…”

Section: Introductionmentioning

confidence: 99%

Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains

Cai

Zhan

et al. 2019

Metals

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Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observations. The results show that the formability can be improved with the increase of temperature, initial stress levels and pre-strains. Deformation mechanisms during stress relaxation of the material were analyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitates of the studied alloy were not sensitive to the age forming conditions, but drastically coarsened at over aging temperature, which decreased the mechanical properties. In addition, the relationship between stress relaxation behavior and aging strengthening is discussed. Based on the dislocation theory and the modified Arrhenius equation, a stress relaxation constitutive equation considering the initial mobile dislocation density and temperature dependent activation energy was established. This model can predict very well the stress relaxation behavior under various temperature, stress level and pre-strain conditions, with an average error of 2%.

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Stress-level-dependency and bimodal precipitation behaviors during creep ageing of Al-Cu alloy: Experiments and modeling

Cited by 109 publications

References 57 publications

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals

The effect of creep aging on localized corrosion resistance of AA2060 alloy

Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains

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