scholarly journals Modelling of liquid film migration in Al-Cu alloys

2022 ◽  
Vol 380 (2217) ◽  
Author(s):  
Hui Fang ◽  
Stephanie Lippmann ◽  
Qingyu Zhang ◽  
Mingfang Zhu ◽  
Markus Rettenmayr
Keyword(s):  
Temperature Gradient ◽  
Liquid Film ◽  
Microstructural Evolution ◽  
Driving Force ◽  
Local Equilibrium ◽  
Grain Structure ◽  
Solid Concentration ◽  
Free Zone ◽  
Cu Alloys ◽  
Liquid Film Migration

Microstructural evolution in the presence of liquid film migration (LFM) is simulated for Al-Cu alloys using a cellular automaton (CA) model. Simulations are performed for the microstructural evolution and concentration distribution in an Al-4 wt.%Cu alloy with initially equiaxed grain structures holding in a temperature gradient. A slight deviation from local equilibrium, estimated from experimental data, is considered to be the driving force for LFM. The direction of LFM is triggered by concentration fluctuations setting a concentration gradient as a further driving force. The simulation successfully reproduces the experimentally observed microstructures generated by LFM accompanied by a particle free zone behind the liquid film. The solid concentration in the particle free zone is found to be the equilibrium solid concentration. The simulated concentration profile across the migrating liquid film agrees well with experimental measurements. The simulated grain structure becomes coarser and highly elongated after holding in the temperature gradient. The results reveal that the increase in transversal grain width is mainly controlled by LFM, while the grain elongation in longitudinal direction is attributed to both LFM and temperature gradient zone melting. The solid concentration decreases from the initial (supersaturated) composition to the local equilibrium solid concentration corresponding to the local temperature. This article is part of the theme issue 'Transport phenomena in complex systems (part 2)'.

Gibbs-Thompson Effect as Driving Force for Liquid Film Migration

2020 ◽  
Author(s):  
Marta Dias ◽  
Marcin Rosiński ◽  
Pedro.C.R. Rodrigues ◽  
José Brito Correia ◽  
Patricia Almeida Carvalho
Keyword(s):  
Liquid Film ◽  
Driving Force ◽  
Liquid Film Migration

Microstructural Evolution in a Commercial Al-Mg-Sc Alloy during ECAP at 300°C

2007 ◽  
Vol 558-559 ◽  
pp. 569-574 ◽  
Author(s):  
Oleg Sitdikov ◽  
Taku Sakai ◽  
Elena Avtokratova ◽  
Rustam Kaibyshev ◽  
Kaneaki Tsuzaki ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Driving Force ◽  
Static Recrystallization ◽  
Grain Structure ◽  
Coarse Grained ◽  
Microstructural Development ◽  
Continuous Dynamic Recrystallization ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Continuous Dynamic

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 300oC (~0.6Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. ECAP at moderate-to-high strains leads to the formation of a bimodal grain structure with grain sizes of around 1 and 8 μm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from a concurrent operation of continuous dynamic recrystallization that occurs during deformation and static recrystallization that occurs during each ECAP cycle by the exposure of the as-deformed material in the die kept at 300oC for around 1.5 minutes. The microstructural development during warm-to-hot ECAP is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to the localization of plastic flow and inhibition of recovery in the present alloy.

Liquid Film Migration in Aluminium Brazing Sheet?

2006 ◽  
Vol 519-521 ◽  
pp. 1151-1156 ◽  
Author(s):  
A. Wittebrood ◽  
S. Desikan ◽  
R. Boom ◽  
Laurens Katgerman
Keyword(s):  
Free Energy ◽  
Corrosion Resistance ◽  
Liquid Film ◽  
Significant Influence ◽  
Clear Explanation ◽  
Distribution Of Elements ◽  
Essential Properties ◽  
Low Levels ◽  
Number Of Publications ◽  
Liquid Film Migration

From literature and own observations it is known that the clad and core alloys that make up aluminium brazing sheet can show severe interaction during the brazing cycle. This interaction leads to a complete re-distribution of elements, changing essential properties like strength and corrosion resistance. This interaction has been reported many times but up to present time no clear explanation is given why this interaction is actually occurring. There are a number of publications addressing the circumstances under which the interaction is more severe. Chemistry and low levels of strain applied before brazing have a significant influence on the severity of the interaction. As a yet possible mechanism behind the interaction Liquid Film Migration is mentioned. The observations done so far are in line with this described mechanism but no ultimate proof has been given so far. The question why the interaction takes place cannot be answered yet, clearly a change of free energy of the system is involved but the mechanism or mechanisms behind the change is unclear.

Microstructure Imaging, Precipitation Formation and Mechanical Properties: Al–Li and Al–Mg–Zn Alloys

2019 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Janos Lendvai ◽  
Hans-Joachim Gudladt
Keyword(s):  
Hydrogen Embrittlement ◽  
Driving Force ◽  
Hydrogen Diffusion ◽  
Nano Particles ◽  
Peak Hardness ◽  
Free Zone ◽  
The Third ◽  
Transmission Electron ◽  
Moisture Conditions ◽  
Precipitation Formation

This article describes concepts of three features of microstructure–properties relationship, first the imaging and formation of nano-particles, then their contribution to hardness, and finally hydrogen embrittlement during fatigue. First, we briefly review the imaging modes in transmission electron microscopy (TEM) for nano-sized precipitates. The next issue is the hardening in Aluminum alloys, which is caused by GP-zones or precipitates, formed at the second step of the annealing process. After homogenization, the peak-hardness can be generally achieved by a few hours of annealing between 120°C and 200°C. Hardness measurements and equal-channel axial pressing (ECAP) showed that even at room temperature the driving force for formation of the particles is so strong that already within one hour of annealing after homogenization a remarkable hardening occurs. The third issue, hydrogen embrittlement, is caused by oxidation of pure Al surfaces produced at the crack tip during fatigue under ambient or wet moisture conditions. The cracks propagate preferentially along the precipitation free zone adjacent to grain boundaries, where hydrogen diffusion is fastest.

Sign in / Sign up

Export Citation Format

Share Document