Investigation on microstructures and properties of arc-sprayed-Al/AZ91D bimetallic material by solid–liquid compound casting

Highlights: • Arc-sprayed-Al/AZ91D bimetallic materials were fabricated by solid–liquid compound casting. • Curved interface had a larger and deeper interface zone than straight interface. • Different characteristics of (Al₁₂Mg₁₇ + δ-Mg) eutectic structure were related to magnesium distribution. • Better straightness of interface could improve both the corrosion resistance and shear strength. The arc-sprayed-Al/AZ91D bimetallic material was fabricated via casting the AZ91D melt into the moulds deposited by arc-sprayed aluminum coating. The microstructures and properties of the arc-sprayed-Al/AZ91D were investigated in this study. Results revealed that there was an interface zone which could be divided into three layers consisting of (Al₁₂Mg₁₇ + δ-Mg) eutectic structure, Al₁₂Mg₁₇ and Al₃Mg₂, respectively. The curved interface had a larger and deeper interface zone containing more Al₁₂Mg₁₇ and Al₃Mg₂ intermetallic compounds than the straight interface. Due to the inhomogeneous distribution of aluminum, magnesium and oxygen, the (Al₁₂Mg₁₇ + δ-Mg) eutectic structure presented four different morphologies, the hardness of which varied from 66 HV to 144 HV. It could be found that the MgAl₂O₄ particles formed after the reactions between the magnesium and alumina may promote the hardness of substrate from 194 HV to 209 HV. The arc-sprayed-Al/AZ91D with straight interface showed higher corrosion resistance and shear strength than the one with curved interface. The results of shear test also indicate that owing to the formation of metallurgical bonding, the adhesive strength between the as-cast AZ91D and arc-sprayed Al coating could be improved by the novel compound casting.