Microstructure and mechanical properties of Zn–15Al-based ternary and quaternary alloys

One binary Zn–15Al, five ternary Zn–15Al–Cu and six quaternary Zn–15Al–3Cu–Si alloys were prepared by permanent mold casting. Their microstructures and mechanical properties were investigated using metallography and hardness, tensile, compression and impact tests. The microstructure of the binary Zn–15Al alloy consisted of β dendrites and α and η phases. The microstructure of ternary Zn–15Al–Cu alloys containing more than 2% Cu revealed ε (CuZn4) particles in addition to the phases present in the binary alloy and the quaternary Zn–15Al–3Cu–Si alloys exhibited silicon particles in addition to the phases present in the ternary alloys. The hardness and compressive strength of these alloys increased continuously with increasing copper and silicon contents. Their tensile strength also increased with increasing copper and silicon contents, but above 3% Cu and 1% Si the trend reversed. However, total percent elongation and impact energy of the ternary and quaternary alloys decreased with increasing copper and silicon contents. T6 heat treatment further increased the hardness and tensile strength of ternary Zn–15Al–3Cu and quaternary Zn–15Al–3Cu–1Si alloys by altering their microstructures. Mechanical test results obtained from the experimental alloys were discussed in terms of their chemical compositions and microstructures. It was concluded that ternary Zn–15Al–3Cu and quaternary Zn–15Al–3Cu–1Si alloys can be successfully substituted for some non-ferrous commercial alloys including ZAMAK and ZA alloys, bronzes and brasses in engineering applications.