Effects of cooling rate and TiB2 addition on the microstructure and properties of Zn-Al4-Cu1 alloy

Abstract

This study aims to enhance the mechanical properties of the hypoeutectic Zn-AlCu alloys, known for their low melting point and good machinability but limited by low tensile strength and brittle fracture behavior. The present research investigates the effect of TiB2 additions in concentrations of 0.2, 0.5, 0.8, and 1.1 wt.% on a Zn-Al4-Cu1 alloy to improve these properties. The alloys were produced by gravity casting into a cast iron mold, and their mechanical properties were analyzed. Additionally, the effects of the cooling rate on the microstructure and secondary dendritic spacing (λ2 ) were analyzed using a stepped mold with different cooling modules. The additions of TiB2 modified the morphology of the primary η-Zn phase and the eutectic constituents (α+η). The optimal mechanical properties were obtained in the Zn-Al4-Cu1 alloy with 0.8% TiB2. Furthermore, increased cooling rates reduced the λ2 in the primary η-Zn phase from 21.4 μm to 11.3 μm. These findings show a manner to enhance the overall properties of Hypoeutectic Zn-Al alloys.