Recent Improvements in Aluminum Brazing Sheet for use in Heat Exchanger Applications, Especially Radiator Tube Stock

Connor, Zayna; Murty, G. S.

doi:10.4271/2005-01-2019

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…With the increasing demand for weight reduction in the automobile industry, the plate fin has been made thinner and thinner. However, it was found that the thin fins could be deformed by their own weight during the brazing process at around 600 • C due to the loss of strength [1][2][3][4][5]. Therefore, the resistance to high temperature deformation of the materials is the most important mechanical property.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Precipitated Particles on the Grain Size in Cold-Rolled Al–Mn Alloy Foils upon Annealing at 100–550 °C

Wang,

Gao,

Xiong

et al. 2024

Materials

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The Al–Mn alloy heat exchanger fin production process includes a brazing treatment at s high temperature of 600 °C, in which coarse grains are preferred for their high resistance to deformation at elevated temperatures by decreasing the grain boundary sliding. In this study, Al-1.57Mn-1.57Zn-0.58Si-0.17Fe alloy foils cold rolled by 81.7% (1.1 mm in thickness) and 96.5% (0.21 mm in thickness) were annealed at 100–550 °C for 1 h to investigate their recrystallization behavior, grain sizes, and precipitates by increasing the annealing temperature, using micro-hardness measurement, electron back-scattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The micro-hardness results showed that the recrystallization finishing temperatures for the two samples were almost the same, 323 ± 2 °C. The EBSD results showed that when the annealing temperature decreased from 550 to 400 °C, the recrystallized grain sizes of the two samples were nearly identical—both increased slightly. Further decreasing the annealing temperature from 400 to 330 °C caused the grain sizes to increase more, with the thinner foil sample having a more significant increase. The SEM and TEM observations showed that the micron-sized primary-phase remained unchanged during the annealing process. The nano-sized secondary phase precipitates formed during the hot-rolling process experienced a coarsening and dissolving process upon annealing. The particle size of the secondary phase increased from 32 nm to 44 nm and the area fraction decreased from 4.2% to 3.8%. The nucleation analysis confirmed that the large primary-phase could act as a nucleation site through particle stimulated nucleation (PSN) mode. The relatively dense secondary phase precipitates with small sizes at lower temperatures could provide higher Zener drag to the grain boundaries, leading to fewer nuclei and thereafter coarser grains. The coarsening of the recrystallized grains in the foils could be implemented through thickness reduction and/or precipitation processes to form densely distributed nano-sized precipitates.

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