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