Interfacial microstructure in joining of arc sprayed Al-Zn coating to AZ91D by solid-liquid compound casting

•Arc-sprayed-Al-Zn/AZ91D was fabricated by solid-liquid compound casting.•The Al-Zn/AZ91D interface has three different intermetallic compounds layers.•The Mg-Al-Zn intermetallic compounds have higher microhardness than AZ91D substrate.

The joining of arc sprayed Al-Zn coating and AZ91D substrate was achieved by solid-liquid compound casting. The microstructure evolution and formation mechanism of the interface were investigated in this study. A scanning electron microscopy (SEM), an energy dispersive spectroscopy (EDS), and an X-ray diffraction (XRD) were used to analyze the microstructure of the Al-Zn/AZ91D interface, whose results showed that the interface could be divided into three different intermetallic compound layers, which confirmed that the bonding between arc sprayed Al-Zn coating and AZ91D substrate was metallurgical. Among the three layers, the layer adjacent to the AZ91D substrate was mainly composed of δ-Mg, Mg17(Al, Zn)12 and a small amount of lamellar Φ-Mg21(Al, Zn)17 intermetallic compounds. The layer which was close to the Al-Zn pseudo-alloy coating mainly consisted of δ-Al, Al2Mg3Zn3 and a small amount of oxides. The intermediate layer was mainly comprised of τ-Mg32 (Al, Zn)49 intermetallic compound. Furthermore, the microhardness values of interface zone were much higher than that of AZ91D substrate.