Microstructure characteristics and mechanical properties of the interface layer of coated steel insert-aluminum bimetals

The effect of aluminizing and Cu electroplating of the steel insert in fabrication of Al-matrix bimetal on the microstructure and mechanical properties of the interface layer was investigated. Compound casting process was used to fabricate Al-matrix bimetals reinforced with coated steel insert. The microstructures at the interface region were studied using light optical and scanning electron microscopes and energy dispersive X-ray spectroscopy. The interfacial shear strengths of the fabricated bimetals were compared using push-out test. The results showed that electroplating with copper and aluminizing of steel insert in aluminum matrix led to significant improvement of metallurgical bonding between the steel and aluminum cast matrix. Cu-coated insert contained a thicker and uniform reaction layer formed at the interface between the steel insert and aluminum matrix compared to aluminized coated insert. The results of push-out tests indicated higher interfacial shear strength for the bimetal with Cu-coated insert despite possessing a larger thickness.