Investigation of a novel automated surface treatment method within accumulative roll bonding of AA6016 sheets

In order to minimize resource utilization and fuel consumption in the transportation and construction sector, possibilities to further enhance the mechanical properties of structural metal alloys are very lucrative. Especially in times of increasing energy costs as well as prices for certain elements, conventional heat treatments as well as alloying routes can be problematic. In this context, purely mechanical methods are capable of providing significant strengthening of already established alloys. Belonging to these methods and especially suitable for sheet metals, is the so-called Accumulative Roll Bonding (ARB) process. It enables the cumulation of the forming degree within the material and can lead to the evolution of an ultrafine grain sized microstructure. However, it severely lacks in its reproducibility and efficiency due to many influencing factors in the process chain. For this, the introduced work focuses on the least investigated step in the process chain, the surface treatment. For this, a novel and automated brushing method is analyzed in terms of its reproducibility as well as feasibility within ARB. Through roughness and topography measurements, it is shown that the force as well as the dwell time of the active brushing contact has a high influence on the resulting surface condition. Additionally, the run-in behavior and the deflection of the brush must be taken into account in order to generate a homogeneous surface finish. By selecting a suitable combination of parameters within the novel surface treatment method, a significant improvement regarding the scattering of the bonding strength is proven. Whereas the conventional manual surface treatment leads to fluctuations of the bonding strength of around 35 %, the newly introduced method displays a clearly reduced deviation of only 1.6 %. This enables to derivate cause-effect relationships between the input parameters regarding brushing, the resulting surface condition and the resulting bonding properties of ARB sheets.