The paper comprises results of examination of the Zn-25 wt % Al alloy grain
refinement by the ZnTi4 modifying master alloy. On the basis of thermal an
alysis, X-ray diffractometry, scanning electron microscopy and light micros
copy it was stated that after modification the examined alloy shows a decre
ase of the undercooling, significant refinement of macrostructure as well a
s significant refinement of the primary dendrites of alpha' ZnAl solid solu
tion. It was also stated that the ZnTi4 master alloy introduces L1(2) TiZn3
particles which act as substrate of the alpha' ZnAl solid solution heterog
eneous nucleation. In the modified melt TiZn3 particles undergo transformat
ion into Ti(Al, Zn)(3) particles which show L1(2) crystal structure and lat
tice parameter very close to that of the alpha' phase. These features make
the Ti (Al, Zn)(3) particles very effective substrate of the alpha' dendrit
es nucleation.