Abstract No.:
5989

 Scheduled at:
Wednesday, May 22, 2019, Saal Brüssel 9:00 AM
Brazing of light metals and intermetallics


 Title:
Surface preparation of the coatings for compound casting of Al-steel sheet hybrids

 Authors:
Leonid Gerdt* / RWTH Aachen University, Germany
Kirsten Bobzin / Surface Engineering Institute, RWTH Aachen University, Germany
Mehmet Oete/ Surface Engineering Institute, RWTH Aachen University, Germany
Stefanie Wiesner/ Surface Engineering Institute, RWTH Aachen University, Germany
Andreas Bührig-Polaczek/ Foundry Institute, RWTH Aachen University, Germany
Johannes Brachmann/ Foundry Institute, RWTH Aachen University, Germany

 Abstract:
Due to the ongoing trend towards light weight constructions within automotive industry joining of dissimilar materials has asserted itself in the last few decades. The combination of steel sheet and aluminum cast is one of the promising approaches to provide a favorable combination of high stiffness and reduced weight. Among different joining techniques the compound high pressure die casting (HPDC) represents a relative novel technology to achieve a desired product performance. Yet, there are still some issues such as poor wetting of steel by aluminum melt and therefore gap formation between the steel sheet and the cast aluminum to be solved.

In the current study coatings of Al-based alloy AA7075 and copper were deposited on the steel with the aim to improve metallurgical bonding between Al-cast and steel. Previous studies showed good prospects of this approach, however the bonding quality and reproducibility should be further improved. In order to control the bonding mechanisms at the interface Al cast/steel sheet surface finishing by grinding with different grit sizes was performed to remove the thermally formed oxide layers which inhibit the wetting by aluminum melt during HPDC. Promising results could be achieved showing a better joint quality and reduced gap formation. Corrosion tests in artificial atmospheres according to ISO 9227:2017 were performed to examine the susceptibility of the Al-steel joints to corrosion. Furthermore, tensile shear tests were carried out to analyze the mechanical properties of the compounds.


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