There is a critical need to understand and optimize the extrudability of AA6xxx
alloys, which are widely used in industries such as automotive and aerospace due
to their favorable combination of strength, formability, and corrosion
resistance. Surface cracking during the extrusion process remains a significant
challenge, compromising the material’s mechanical properties and product
quality. While previous studies have investigated surface cracking using various
techniques, the underlying mechanisms remain elusive, especially regarding the
role of important alloying elements such as copper. Therefore, this research
provides a thorough investigation of the effect of copper additions on the
solidus temperature, hot deformation behavior, and extrudability of AA6xxx
alloys. Using experimental and numerical methods, the material’s solidus
temperature and constitutive behavior were determined. Extrusion trials were
conducted for alloys with different copper levels using a flat die over a range
of extrusion speeds, with the resulting surface defects being examined. The
findings indicate that although the copper content had little impact on the hot
compression behavior, it did affect the solidus temperature. Alloys with a
higher level of copper had a lower solidus temperature, and hence, the maximum
extrusion speed for a given temperature was lower. Numerical simulations
demonstrated that surface cracking occurred once the surface temperature of the
alloy reached 96% of the solidus temperature. This study contributes to the
optimization of extrusion processing by highlighting the role of copper in
improving the extrudability of high-strength AA6xxx aluminum alloys, offering
insights for developing higher-quality alloy products.
