Enhanced Mechanical Properties by Directional Solidification and Cold Drawing in Cu Added Zn-Al Alloys

초록

The lamellar structure of two phases, the Zn-rich and Al-rich phases, is formed in a Zn-5 wt% Al eutectic alloy. In order to study the effect of microstructural changes on the tensile properties of eutectic Zn-Al binary alloy, Zn-Al and Zn-Al-Cu alloys were directionally solidified at a growth rate of 50 mu m/s using a Bridgman-type method. The alloys were successively drawn until reaching area reductions of 50% and 80% at room temperature. The tensile strength of the Zn-Al alloy decreased with increasing drawing ratio. In the Zn-Al-Cu alloy, the tensile strength increased until the area reduction reached 50%, but decreased at an area reduction of 80%. The ductility of alloys prepared by directional solidification increased with increasing drawing ratio. The orientations of the lamellar structure and grains were aligned in the drawn direction. The inter-lamellar distance of the alloys also decreased with increasing drawing ratio. As a result, the trade-off between strength and ductility could be significantly reduced. The strength and ductility combination of 246 MPa-40% was achieved by cold drawing with 80% area reduction of the Zn-Al-Cu alloy.

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