Non-isothermal creep aging behaviors of an Al-Zn-Mg-Cu alloy

Lei, Chao; Li, Hengyun; Fu, Jiawei; Bian, T.J.; Zheng, G.W.

doi:10.1016/j.matchar.2018.08.005

Cited by 24 publications

(14 citation statements)

References 34 publications

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“…It is well established by a number of researchers, including Lei et al [16,17] and Li et al [18,19], etc., that the power-law creep Equation, Equation (1), may be used to describe dislocation creep behavior. Therefore, the n value in Equation (2) can be derived from Equation (1), which is plotted (on a log-log axis) in Figure 3.…”

Section: Creep Behaviormentioning

confidence: 97%

Study on Multi-Step Creep Aging Behavior of Al-Li-S4 Alloy

Xia

Zhan

et al. 2019

Metals

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Creep age forming (CAF) is a new technology developed for manufacturing large aluminum components in the aerospace industry. Aluminum–lithium alloys may be used in aerospace components because of their high modulus, specific strength and specific stiffness. Therefore, the creep deformation, mechanical properties and aging precipitation of Al-Li-S4 alloy under CAF conditions were studied. It was found that the creep behavior presents double steady state creep stages during the creep aging process. With the increase of stress level, the first steady creep rate increased, but the second steady creep rate was slightly reduced. Coincidentally, in the first steady state creep stage, the yield strength of the studied alloy also showed a slow increase stage. TEM observation showed that Al-Li-S4 alloy mainly contains two precipitation phases, T1 phase and θ’ phase. A few precipitates form during the first steady creep stage. Then, a lot of nucleation and growth of T1 phase resulted in rapid increase of yield strength. At the same time, the increase of stress level effectively inhibited the growth of T1 phase, which resulted in these strengthening phases being more uniform, and thus improved the mechanical properties of materials. On this basis, the relationship between the multi-step behaviors of creep, mechanical properties and aging precipitates are discussed. It is considered that the main reasons for the multi-step phenomenon of creep and mechanical properties are strongly related to the nucleation, growth and distribution of T1 phase.

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Section: Creep Behaviormentioning

confidence: 97%

Study on Multi-Step Creep Aging Behavior of Al-Li-S4 Alloy

Xia

Zhan

et al. 2019

Metals

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“…E(T) represents that Young s modulus is function of temperatures. The experimental data and fitting curves for Equation (8) are shown in Figure 8a Q c is the apparent activation energy. Generally, when the temperature range is narrow, it is considered to be simply unaffected.…”

Section: Deformation Mechanism During Stress Relaxation Aging Processmentioning

confidence: 99%

“…The power-low equations describe a function of steady-state creep rate on stress, temperature and grain diameter in pure metals [6]. However, for aluminum alloys, the grain structure and average size are not significantly altered, since the aging temperature is much lower than the recrystallization temperature [7,8]. Therefore, the subsequent studies on stress relaxation of aluminum alloys focused on stress, temperature.…”

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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“…Recent studies on NIA treatments of aluminium alloys showed that the mechanical properties and corrosion resistance were improved by NIA [23][24][25]. Compared with T6 specimens, NIA-treated Al-Cu-Mg-Si specimens had a higher density of fine, shearable θ′ precipitates because of the secondary precipitation during cooling, which enhanced the mechanical properties and afforded excellent low-cycle fatigue performance [26].…”

Section: Introductionmentioning

confidence: 99%

Microstructure, corrosion behavior and mechanical properties of a non-isothermal ageing treated cast Al–4.5Cu–3.5Zn–0.5Mg alloy

Wang

Jiang

et al. 2020

Mater. Res. Express

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Al-Cu, being a high-strength aluminium alloy, is used to prepared castings which are widely used in the automotive and aerospace industries as lightweight parts. However, corrosion is an issue. The Al-Cu alloys show improved properties when other elements are added to them. One such alloy is Al-4.5Cu-3.5Zn-0.5Mg. In order to improve the corrosion resistance and strength of this Al-4.5Cu-3.5Zn-0.5Mg cast alloy, a novel non-isothermal ageing (NIA) treatment was developed that comprised a heating stage up to 250°C, followed by a cooling stage down to room temperature at the rate of 60°C·h −1 . Specimens were removed throughout the process and immediately quenched for morphological, mechanical, and electrochemical testing. The hardness continuously increased up to 124 HV with ageing time. The alloy exhibited optimal properties after ageing for~340 min (with the aging temperature reaching 130°C during the cooling stage of the NIA treatment), with a tensile strength and maximum corrosion depth of 395 MPa and 165 μm, respectively. Fine precipitates discontinuously appeared at the grain boundaries during the cooling stage. Some new fine Ω phases were precipitated in the grains, thereby narrowing the precipitation-free zone. Thus, high strength and good corrosion resistance of the alloy can be obtained via the NIA treatment. Notably, NIA treatments are less time-consuming than isothermal ageing treatments, thereby expanding the applications of high-strength cast aluminium alloys in the manufacturing industry.

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Non-isothermal creep aging behaviors of an Al-Zn-Mg-Cu alloy

Cited by 24 publications

References 34 publications

Study on Multi-Step Creep Aging Behavior of Al-Li-S4 Alloy

Study on Multi-Step Creep Aging Behavior of Al-Li-S4 Alloy

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

Microstructure, corrosion behavior and mechanical properties of a non-isothermal ageing treated cast Al–4.5Cu–3.5Zn–0.5Mg alloy

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