Abstract
Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the Al-Si (Mn, Mg) system, which have limited weldability. The mechanical joinability of the cast components depends on their ductility, which is influenced by the microstructure. High-strength cast aluminium alloys have relatively low ductility, which leads to cracking of the joints. This limits the range of applications for cast aluminium alloys. In this study, an aluminium alloy of the Al-Si system AlSi9 is used to investigate relationships between solidification conditions during the sand casting process, microstructure, mechanical properties, and joinability. The demonstrator is a stepped plate with a minimum thickness of 2.0 mm and a maximum thickness of 4.0 mm, whereas the thickness difference between neighbour steps amounts to 0.5 mm. During casting trials, the solidification rates for different plate steps were measured. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties and the mechanical joinability are investigated.
Highlights
Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials
Realisation of mixed construction concepts in modern automotive engineering requires the joining of sheet metal and extruded profiles with cast components made of different materials
This study aims to establish relationships between solidification conditions in sand casting, microstructure parameters, mechanical properties, and joinability to prevent cracks in the closing head during clinching
Summary
Realisation of mixed construction concepts in modern automotive engineering requires the joining of sheet metal and extruded profiles with cast components made of different materials. The advantage of cast components for lightweight moulding is that the structure can be optimally adapted to the applied force and have good mechanical properties [1,2,3,4]. Cast aluminium alloys are characterised by low melting temperature, good surface quality, castability, and low gas absorption, with the exception of hydrogen [5]. Since weight reduction is desired, these castings are usually made of high-strength aluminium alloys of the Al-Si (Mn, Mg) system. The weldability of cast aluminium alloys proves to be problematic [6]. Since high-strength cast aluminium alloys, such as AlSi10Mg or AlSi5Cu3Mg, have relatively low ductility, it is often not possible to produce a crack-free joint when using mechanical joining processes
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