Effects of Zn Interlayer on Microstructures and Mechanical Properties of TC4/AZ91D Bimetal via Solid–Liquid Compound Casting Process

The solid–liquid compound casting (SLCC) was used to produce Ti/Mg bimetal via hot dip Zn coating, and the interfacial microstructures and mechanical properties of the Mg/Ti bimetal were investigated in this work. The scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) reveal that there is no interlayer metallurgical reaction when the pouring temperature is 670 °C. As the pouring temperature increases to 710 and 750 °C, the thickness of the metallurgical interfacial zone is about 130 and 310 µm, respectively. The interfacial zone is mainly consists of α -Mg and τ -TiAlZn coexistence phases. Thermodynamic models are established to explain the evolution mechanism of α -Mg and τ -TiAlZn coexistence phases. It is concluded that the formation process of α -Mg and τ -TiAlZn phase coexist is as follows: TiZn 5 (s)-to-TiZn 5 (l), and then α -Mg and τ -TiAlZn phases coexist. While the sequence of the phases that formed in the Ti–Al–Zn ternary system is TiAl 3 → τ -TiAlZn, this is based on the fact that the Al atoms are used up at the interfacial zone. The highest shear strength of Zn-coated TC4/AZ91D bimetallic material is up to 34.24 Mpa when the pouring temperature is 710 °C.