Precipitate formation in aluminium alloys: Multi-scale modelling approach

Kleiven, David; Akola, Jaakko

doi:10.1016/j.actamat.2020.05.050

Cited by 26 publications

(15 citation statements)

References 29 publications

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“…While the vacancy-solute complex that appeared in Al 83 Mg 12 Si 12 is not VMg 4 Si 8 but VMg 4 Si 7 , the central Mg atom in the top Mg layer completely shifts to the Si layer. In contrast, the structure of Al 84 Mg 12 Si 12 , in which a vacancy is not included, exhibits an L1 0 -like layered structure, which agrees with the result of a multiscale approach [15]. If a Mg vacancy is formed in the L1 0 structure, the local structure around the Mg vacancy becomes similar to that of the layered VMg 4 Si 8 complex.…”

Section: Resultssupporting

confidence: 82%

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Structural Transition of Vacancy–Solute Complexes in Al–Mg–Si Alloys

Mizuno

Sugita

Araki

2021

Metals

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To theoretically examine the structural transition of vacancy–solute complexes in Al–Mg–Si alloys, we performed first-principles calculations for layered vacancy–solute complexes with additional Mg atoms. The central Mg atom in the additional Mg layer shifted to the Si layer with the increase in the number of Mg atoms to weaken the repulsive Mg–Mg interaction and to form Mg–Si bonds. When five Mg atoms were added to the layered vacancy–solute complex, the central Mg atom completely shifted to the Si layer, and a Mg vacancy was formed in the Mg layer, which indicated that the β″-eye is formed upon the addition of Mg atoms. We reproduced β″-eye formation from a solid solution with a vacancy using first-principles-based Monte Carlo simulations. Once the β″-eye was formed on the layered vacancy–solute complex, the process can be repeated by the formation of alternate Mg and Si layers along [010] β″. These results clearly indicate that the layered vacancy–solute complex plays an important role in β″-eye formation.

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Section: Resultssupporting

confidence: 82%

“…However, the structural transition to the β phase remains unclear. The formation of a layered MgSi phase in an Al matrix was reported using a multiscale approach [15]. However, the formation of the β phase, which requires a shift of Mg atoms to the Si layer, was not observed.…”

Section: Introductionmentioning

confidence: 99%

Structural Transition of Vacancy–Solute Complexes in Al–Mg–Si Alloys

Mizuno

Sugita

Araki

2021

Metals

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“…According to the Orowan relationship (Figure 9), larger inter-particle spacing results in a decrease in the resistance to dislocation motion thereby facilitating the occurrence of Orowan looping. The increased deformability of the matrix via the easy dislocation motions leads to reduced strength and subsequently diminished quality index values in the castings [24][25][26][27][28][29][30]. Aging at lower temperature results in formation of precipitates; with fine sizes, high density and lower inter-particle spacing.…”

Section: Stage Imentioning

confidence: 99%

Generation and Relaxation of Residual Stresses in Automotive Cylinder Blocks

Mohamed¹,

Samuel²,

Doty³

et al. 2021

Advanced Applications of Hydrogen and Engineering Systems in the Automotive Industry

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There is direct proportionality between ultimate tensile stress (UTS) and residual stresses (RS). Residual stresses gradually decrease with decreasing cooling/quenching rates. Quenching in cold water develops highest, whereas air cooling produces lowest, residual stresses. Significant increase in RS is observed in specimens with low dendrite arm spacing (high solidification rate), while lower residual stresses are measured in specimens with high dendrite arm spacing (low solidification rate). For I-4 and V-6 engine blocks, there is refinement in microstructure due to the increase in solidification rate along the cylinder length. The developed residual stresses are normally tensile in both engine types. Air cooling following solution heat treatment produces higher RS compared to warm water and cold water quenching. Solution heat treatment and freezing lead to maximum RS relaxation where 50% of the stresses are reduced after the solution heat treatment step. Aging time and temperature are directly proportional to the residual stresses relaxation. Relaxation of RS also depends on the geometry and size of the workpiece. It should be mentioned here that the I-4 and V-6 cylinder blocks were provided by Nemak-Canada (Windsor-Ontario-Canada). Residual stress measurements technique and procedure are typical of those used by the automotive industry in order to provide reliable data for industrial applications supported by intensive experiments.

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“…To fully describe crystalline materials in the real world however, we require a description of both the crystal lattice, and all defects present in a given material. These include point defects such as dopants, vacancies, or interstitials (Dederichs et al, 1978), line defects such as dislocations (LeSar, 2014), planar defects including internal boundaries and surfaces (Tang et al, 2006), and volume defects such as precipitates (Kleiven & Akola, 2020). Strain fields in the surrounding material can be induced by each of these defects, or generated by the boundary or growth conditions of the material such as in thin film stresses (Janssen, 2007).…”

Section: Introductionmentioning

confidence: 99%

Automated Crystal Orientation Mapping in py4DSTEM using Sparse Correlation Matching

et al. 2022

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Crystalline materials used in technological applications are often complex assemblies composed of multiple phases and differently oriented grains. Robust identification of the phases and orientation relationships from these samples is crucial, but the information extracted from the diffraction condition probed by an electron beam is often incomplete. We have developed an automated crystal orientation mapping (ACOM) procedure which uses a converged electron probe to collect diffraction patterns from multiple locations across a complex sample. We provide an algorithm to determine the orientation of each diffraction pattern based on a fast sparse correlation method. We demonstrate the speed and accuracy of our method by indexing diffraction patterns generated using both kinematical and dynamical simulations. We have also measured orientation maps from an experimental dataset consisting of a complex polycrystalline twisted helical AuAgPd nanowire. From these maps we identify twin planes between adjacent grains, which may be responsible for the twisted helical structure. All of our methods are made freely available as open source code, including tutorials which can be easily adapted to perform ACOM measurements on diffraction pattern datasets.

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Precipitate formation in aluminium alloys: Multi-scale modelling approach

Cited by 26 publications

References 29 publications

Structural Transition of Vacancy–Solute Complexes in Al–Mg–Si Alloys

Structural Transition of Vacancy–Solute Complexes in Al–Mg–Si Alloys

Generation and Relaxation of Residual Stresses in Automotive Cylinder Blocks

Automated Crystal Orientation Mapping in py4DSTEM using Sparse Correlation Matching

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