On the Effect of Stress on Nucleation, Growth, and Coarsening of Precipitates in Age‐Hardenable Aluminum Alloys

Skrotzki, Birgit; Murken, J.

doi:10.1002/9781118787922.ch5

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…following input parameters are used in all simulations: The time step dt and grid space dx are chosen as 1 s and 3 nm, respectively. The simulations are performed at 473 K where Li in Al has a diffusion coefficient of D = 1.2 × 10 −18 m 2 s −1 and an atomic mobility of M = D/RT = 3.4 × 10 −22 mol m 2 J −1 s −1[76]. The simulation box sizes are chosen as (64 dx)3 .…”

mentioning

confidence: 99%

Numerical Benchmark of Phase-Field Simulations with Elastic Strains: Precipitation in the Presence of Chemo-Mechanical Coupling

Kamachali

Schwarze

Lin

et al. 2018

Computational Materials Science

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Phase-field studies of solid-state precipitation under strong chemo-mechanical coupling are performed and benchmarked against the existing analytical solutions. The open source software packages OpenPhase and DAMASK are used for the numerical studies. Solutions for chemical diffusion and static mechanical equilibrium are investigated individually followed by a chemo-mechanical coupling effect arising due to composition dependence of the elastic constants. The accuracy of the numerical solutions versus the analytical solutions is quantitatively discussed. For the chemical diffusion benchmark, an excellent match, with a deviation < 0.1%, was obtained. For the static mechanical equilibrium benchmark Eshelby problem was considered. In this case, a deviation of 5% was observed in the normal component of the stress, while the results from the diffuse interface (OpenPhase) and sharp interface (DAMASK) models were slightly different. In the presence of the chemomechanical coupling, the concentration field around a static precipitate was benchmarked for different coupling coefficients that represent the strength of composition dependency of elastic constants. It is found that the deviation increases proportional to the coupling coefficient. Finally, the interface kinetics in the presence of the considered chemo-mechanical coupling were studied using OpenPhase and a hybrid OpenPhase-DAMASK implementation, replacing the mechanical solver of OpenPhase with DAMASK's. The observed deviations in the benchmark studies are discussed to provide guidance for the use of these results in studying further phase transformation models and implementations involving diffusion, elasticity and chemo-mechanical coupling effect.

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mentioning

confidence: 99%

Numerical Benchmark of Phase-Field Simulations with Elastic Strains: Precipitation in the Presence of Chemo-Mechanical Coupling

Kamachali

Schwarze

Lin

et al. 2018

Computational Materials Science

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“…Especially at the relatively high aging temperature considered here, the precipitation kinetics already are very fast despite the additional employment of superimposed stress. In addition to the impact of superimposed external stresses on the sizes and morphologies of precipitates, stress-aging leads to the reduction of lateral dimensions of PFZs as reported in previous studies [18,67,68]. In these studies, all focusing on Al-Cu-Mg-Ag and Al-Cu alloys, high degrees of strain during stress-aging were employed resulting in the introduction of dislocations as preferential sites for the nucleation of second phases.…”

Section: Heat Treatment-microstructure-property Relationshipsmentioning

confidence: 97%

Effects of Aging under Stress on Mechanical Properties and Microstructure of EN AW 7075 Alloy

Sajadifar

Krooß

Fröck

et al. 2021

Metals

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In the present study, microstructural and mechanical properties of EN AW 7075 following stress-aging were assessed. For this purpose, properties of stress-aged samples were compared with values obtained for conventionally aged counterparts. It is revealed that the strength and hardness of EN AW 7075 can be increased by the presence of external stresses during aging. Precipitation kinetics were found to be accelerated. The effects of conventional and stress-aging on the microstructure were analyzed using synergetic techniques: the differently aged samples were probed by differential scanning calorimetry (DSC) in order to characterize the precipitation processes. DSC was found to be an excellent screening tool for the analysis of precipitation processes during aging of this alloy with and without the presence of external stresses. Furthermore, using electron microscopy it was revealed that an improvement in mechanical properties can be correlated to changes in the morphologies and sizes of precipitates formed.

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“…The effects of transformation strains and external stresses on the evolution of precipitates in Al alloys are widely known [22,23,24,25,26,27,28,29,30]. For the T 1 precipitate, it is known that dislocations may play a role in both nucleation and growth.…”

Section: Introductionmentioning

confidence: 99%

Thickening of T1 Precipitates during Aging of a High Purity Al–4Cu–1Li–0.25Mn Alloy

et al. 2018

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The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of these two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates.

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On the Effect of Stress on Nucleation, Growth, and Coarsening of Precipitates in Age‐Hardenable Aluminum Alloys

Cited by 5 publications

References 25 publications

Numerical Benchmark of Phase-Field Simulations with Elastic Strains: Precipitation in the Presence of Chemo-Mechanical Coupling

Numerical Benchmark of Phase-Field Simulations with Elastic Strains: Precipitation in the Presence of Chemo-Mechanical Coupling

Effects of Aging under Stress on Mechanical Properties and Microstructure of EN AW 7075 Alloy

Thickening of T1 Precipitates during Aging of a High Purity Al–4Cu–1Li–0.25Mn Alloy

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