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Nikkhah Fini, Sheida

University of British Columbia

Recently, there is an increase in demand for the usage of aluminum extrusion alloys in automotive applications to reduce the vehicle weight. Bendability (i.e. how much bending the material can sustain without cracking) is an important material property, both for the forming of components and in crash behavior. During the production of Al-Mg-Si extrusion alloys (AA6082 non- recrystallized) which was studied in this research, the properties of the surface can be substantially different from those of the interior as these alloys are prone to forming a surface layer known as the Peripheral Coarse Grain (PCG) zone. The objective of this study is to investigate the effect of the PCG layer thickness on bendability of aluminum alloys. Different PCG layers thicknesses were achieved in the range of 50 μm to 800 μm at different extrusion ram speeds by our industry partner. In this project, different mechanical tests were done to characterize the effect of PCG layer thickness, and heat treatment on the bendability of aluminum extrusion alloys. The microstructures were examined using Barker’s etch to observe the initiation of cracks in bend region. To see the effect of PCG layer on the bendability, the PCG layer was removed from one side of the sample and then the test was conducted with the PCG layer in tension and compression. The results show that the sample with a very thin PCG layer (50μm) showed similar load- displacement curves whether the PCG layer was in compression or tension. However, for the thicker PCG layers, the bend response was poorer when the PCG layer was in tension. Tests done on the samples in ED and TD direction (Note: ED- bend axis ⊥ to extrusion direction, TD- bend axis ∥ to extrusion direction) and results show that for all thicknesses of the PCG layer, tests done in TD direction showed a lower bend angle failure compared to the tests done in ED direction. Finally, to see the effect of cooling rate on bendability, cooling rate of 13-20 °C/s was chosen and after bend test the results showed that the lower cooling rate had 10-20% poorer bendability.

Text

2023-04-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84443

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/