PHASES OF HETEROGENEOUS NUCLEATION IN THE ZNAL25 ALLOY MODIFIED BY ZN-TI AND AL-TI MASTER ALLOYS

The subject of the present investigation is the identification of the Ti-Zn-Al ternary phase which takes part in hetero geneous nucleation o f primary alpha' dendrites in the ZnA125 alloy. On the basis of light microscopy, diffractometry and microprobe analysis it is concluded tha t the ternary phases Ti(Zn,Al)(3) and (Ti,Zn)(5)Al-11 are present in t he centres of grain refined alpha' dendrites. These ternaries are cons idered to be active nuclei of alpha'. The presence of Ti(Zn,Al)(3) in the microstructure of ZnA125 modified by ZnTi4 shows that Ti(Zn,Al)(3) can be produced by binary Ti-Zn as well as by binary Ti-Al.