WEB Mechanical joinability of aluminum sand cast componentsTuesday (22.09.2020) 10:25 - 10:40 Z: Special Symposia II Part of:
The implementation of mixed-material construction concept in modern automotive engineering requires the connection of sheet metal or extruded profiles with cast components made of different materials. Due to the desired weight reduction, these cast components are usually manufactured from high-strength age-hardenable aluminum alloys of the Al-Si-(Mg)-system, which exhibit a limited weldability. The mechanical joinability of the cast components depends on their ductility that is influenced by the microstructure. High-strength age-hardened casting aluminum alloys such as AlSi10Mg have a relatively low ductility, which causes cracking of the joints. This limits the spectrum of casting aluminum alloys application.
A promising solution to avoid cracking during mechanical joining could be grading of the microstructure in cast components localized at areas of projected joints. The grading can be realized by a local heat treatment or by an adaptation of solidification conditions, which result in a significant increase of ductility and improve the mechanical joinability of aluminum cast parts.
The topic of current research activities is establishing of relationships between solidification conditions during sand casting, microstructure parameters, mechanical properties and joinability. In this study, two aluminum alloys of the Al-Si-system AlSi9Mn and AlSi10Mg are utilized. The latter alloy belongs to the group of high-strength age-hardenable alloys. The demonstrator is a stepped plate with a minimum thickness of 2,0 mm and maximum thickness of 4,0 mm, whereas the thickness difference between neighbor steps amounts to 0,5 mm. During casting trials, the solidification rates for different plate steps were evaluated. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties of different demonstrator elements as well as their mechanical joinability by means of clinching are investigated.