Interface characterization of aluminium casting reinforced steel inserts

During the last years, new technologies have been developed in order to reduce the environmental pollution and preserve resources. For this reason, the light weight concept has aroused highly interesting in the transportation industry, particularly, in the development of electric and hybrid vehicles.

One of the actions was to replace some components made of steel or cast iron by other made of aluminium casting. However, some components cannot be replaced only by aluminium and 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.

This work is a comparative study of different interfaces os S355J2H steel insert in AlSi7Mg aluminium cating. To develop this research, a range of processing conditions for improving the bond strength between steel insert and aluminium alloy were carried out. Before casting, different chemical, thermal and emchanical treatments were applied to the steel insert: As-received condition, pre-heating, shot blasting, pickling, hot dip aluminizing, hot dip galvanizing, zinc coating. The steel/AlSi7Mg interfaces were characterized by optical microscopy (LOM), sanning electro microscopy (SEM) and X-ray diffraction (XRD). Special attention was paid to study the interface failure position and the intermetallic phases and compounds formed in the reaction action zone.

The interface shear strenght has been assessed by the push-out test, and the results have been correlated with microstructural observations at the interfaces.