Effect of Ti addition on microstructure and mechanical properties of Zn-22Al alloy after ECAP

Abstract

The effect of Ti addition on microstructure and mechanical properties of Zn-22Al eutectoid alloy with 0.15 wt% Ti was investigated. It was observed that the presence of Ti changes the morphology of η phase in the alloy. Addition of Ti to Zn-Al alloy caused the formation of Ti(Zn,Al)₃ phase. Before applying equal channel angular pressing (ECAP), two times of homogenization treatment were conducted on the alloy. After secondary homogenization, the microstructure consisted of a homogeneous and fine mixture of α and η phases and the as-cast lamellar structure removed. After homogenization, ECAP was carried out on Ti-containing Zn-22Al alloy. The fraction of high angle grain boundaries increased with increasing the number of ECAP passes. The average grain size reduced from 930 nm after secondary homogenization to 380 nm after 8 passes of ECAP. The texture of the alloy also changed by applying ECAP. Maximum elongation to failure of the homogenized alloy was 135% at a strain rate of 10⁻⁵ s⁻¹ which enhanced to a maximum of 405% at a strain rate of 10⁻³ s⁻¹ after 8 passes of ECAP. It was also observed that by conducting ECAP and increasing the number of passes the hardness decreases, which indicates work-softening behavior due to dynamic recovery/recrystallization.

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