ã€China Aluminum Industry Network】 After the extrusion of aluminum profiles, it's common to observe a ring of coarsely grained material along the outer edge of the profile. This phenomenon can negatively affect the mechanical properties of the final product. The formation mechanism and influencing factors behind these coarse-grained rings are quite complex, and there is still no universally accepted explanation in the industry. One possible reason is that the metal isn't deformed uniformly during extrusion. The outer layer experiences significant friction with the die wall, leading to greater deformation. Additionally, impurities from the tail end of the billet may be drawn into the outer layer, contributing to the formation of larger grains.
During heat treatment, the surface layer of the extruded part is exposed to high temperatures for extended periods. This environment, combined with the presence of impurities, promotes grain growth, making the outer layer's microstructure significantly coarser than the inner regions.
To minimize or eliminate the formation of these coarse-grained rings in finished aluminum products, several strategies can be applied:
1) Using the reverse extrusion technique helps achieve more uniform deformation, reducing the likelihood of forming a coarse-grained ring.
2) Adding small amounts of elements like manganese, iron, and titanium to the alloy can help reduce or even eliminate the formation of these rings by altering the microstructure.
3) Performing high-temperature extrusion within the single-phase region of the alloy can help reduce the depth of the coarse-grained zone.
4) Increasing the size of the extrusion residue can prevent non-metallic inclusions from being carried into the final product, thus reducing the risk of grain coarsening.
5) Ensuring that the inner walls of the extrusion container remain clean and smooth allows for the formation of a complete aluminum sleeve, which reduces friction and improves material flow during extrusion.
6) Avoiding excessively high quenching temperatures can prevent unnecessary grain growth during the cooling process.
7) Employing porous dies can improve material flow and distribution, helping to avoid localized deformation that might lead to coarse grains.
By implementing these measures, manufacturers can significantly enhance the quality and performance of extruded aluminum profiles, ensuring they meet the required mechanical and structural standards.
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Zhoushan Jinsheng Bimetallic Plastic Machinery Factory , https://www.jinshenggalloy.com