Influences of Coating Type on Microstructure and Strength of Aluminum–Steel Bimetal Composite Interface

The present study is aimed to investigate the effects of zinc electroplated coating and hot dipping at 480 °C on the microstructure and mechanical properties of pure aluminum/40NiCrMo2-2 steel bimetal interface produced by compound casting at 780 °C. Accordingly, microstructural studies and interface shear strength were determined using optical microscope, scanning electron microscope, and push-out test. Results showed that the interface layer in all the samples, independent from the coating type, is composed of two sub-layers of Fe2Al5 and FeAl3. Furthermore, the linear analysis results and elemental distribution map of the interface indicated that no considerable amount of zinc was present in the interface of the samples. Based on the results, the maximum strength was related to the electroplated sample with the value of 45.1 MPa, while the hot-dipped sample had the strength of 37.5 MPa, which was attributed to the formation of interface layer with less defects in the electroplated sample.