Primary AlSi10MnMg alloy is the most widely used alloy for manufacturing of vacuum assisted high pressure die castings (VPDC) with high ductility requirements. In this alloy, die soldering is avoided by a high Mn level (0.5 - 0.6 wt. %) while Fe is kept low (< 0.25 wt. %). Such combination guarantees that the Al-Fe-Mn-Si intermetallic compounds are of the α-iron rich polyhedral or Chinese script type, which is less harmful to the ductility. However, secondary alloys are cheaper and their production requires less energy than the one of primary alloys. The higher amount of Fe, a common impurity in secondary alloys, reduces ductility but also die soldering and thus manufacturing costs. Microadditions based on Mn are known to be very effective in transforming the harmful needle/platelet shaped β-compounds into α-iron compounds with a less harmful morphology. In this work a secondary alloy with 0.60 wt. % Fe and different Mn microadditions has been cast in test parts with different wall thicknesses using VPDC technology. The Mn content of the new alloy has been optimized. Mechanical properties of the optimised alloy have been determined in different heat treatment conditions and been compared to the corresponding AlSi10MnMg primary alloy. Mechanical properties similar to those of the primary alloy have been achieved.

The necessity of preserving resources and to reduce environmental pollution makes light weight concepts highly interesting for the transportation market, with light weight being essential for newly developed electric and hybrid vehicles. However, some components cannot be replaced only by aluminium, but need to be combined with steel in order to achieve the desired mechanical characteristics. Therefore, there is great interest in developing processes to manufacture aluminium/steel hybrid structures that present a good bond.In the present work a range of processing conditions for improving the bond strength between S355J2H steel inserts and AlSi7Mg casting alloy were investigated. Before casting, different chemical, thermal and mechanical treatments were applied to the steel insert: As-received condition, preheating, shot blasting, pickling, hot dip aluminizing, hot dip galvanizing, zinc coating and nickel/copper plating. The steel/AlSi7Mg interfaces were characterized by optical microscopy (LOM), scanning electron microscopy (SEM) and x-ray diffraction (XRD). Special attention was paid to the presence of defects, formation of oxides and/or intermetallic phases in the reaction zone. The interface shear strength has been assessed by the push-out test, and the results have been correlated with microstructural observations at the interfaces. Combinations of different insert treatments were also investigated.

This work has the purpose to demonstrate that if an adequate melt treatment is applied, it is pos-sible to obtain recycled aluminium alloy AlSi10MnMg(Fe) with as good metal cleanliness than primary AlSi10MnMg alloy. The melt quality is assessed by the thermal analysis, density index, macro- and micro-inclusions tests, of one primary and two secondary alloys, before and after the melt treatment. The melt treatment is based on deoxidation, degassing and skimming with de-tailed procedure described in this article. The different analysis are: Thermal analysis to compare the variables of the solidification cooling curve (Al primary temperature and its undercooling; Al-Si eutectic temperature and its recalescence); Density index is used to evaluate the hydrogen gas content in the melt; Macroinclusions level is analysed after solidifying the melt under vacuum of 5 mbar, favouring inclusion floatation to the sample surface; Microinclusion level is evaluate with porous disc filtration apparatus (similar to PoDFA).