Effect of cast iron surface treatment on interfacial adhesion of Al/Fe compound cast structure
Typ
Examensarbete för masterexamen
Program
Publicerad
2020
Författare
Heshmati, Nader
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Development of the light weight material is necessary for cost optimization and reducing
environmental pollution in the automotive industry. However, the aluminum
solely does not provide the desired mechanical properties such as wear-resistance and
stiffness and it is needed to be combined with ferrous inserts. Compound casting is
used as the joining method of Al/Fe components due to its cost-efficiency in which
molten aluminum is solidified around a solid ferrous insert to form a metallurgical
bonding at the Al/Fe interface. This Metallurgical bonding provides the integrity of
the component, and therefore requires to be strong enough to withstand all stresses
during the casting process as well as the consumption stage. The formation of a
compact reaction layer is restricted by the wetting behaviour of the aluminum and
oxide formation on the insert and the aluminum.
In this study, the effect of different cast iron insert surface treatments on the bond
formation of the interface between cast iron and AlSi7Mg were investigated. As-cast
condition, cleaning, etching, sandblasting, hot-dip galvanizing, acidic zinc plating,
hot-dip aluminizing, and thermal spraying samples were pre-heated, followed by
gravity casting in a pre-heated mold. The Al/Fe interface was studied by optical
and scanning electron microscope (SEM) with a focus on the formation of the oxide
and diffusion reaction layer. The results indicated that the diffusion layer formation
was suppressed due to the presence of an oxide layer that was formed during the preheating
stage. The shear strength of the Al/Fe interface was assessed by the pushout
test and the result was compared with microstructural changes at the interface.
The correlation between the surface roughness of the inserts, their microstructure,
and mechanical properties was also discussed. Based on the obtained result, a new
cast experiment has been designed by blasting+aluminizing of the cast iron insert,
removing the pre-heating, and instant casting after the aluminizing process to ensure
the formation of the metallurgical bonding during the compound casting.
Beskrivning
Ämne/nyckelord
Cast iron inserts , Interface reaction layer , Interface shear strength , Al/Fe Compound casting