Abstract: An additive of Y to Ni_3Al based alloy may form a phase YNi_5 which increases in amount with the increase of Y content.It was found that the YNi_5 phase in Ni_3Al alloy could remarkably make its grains finer and its grain boundaries more crooked other than straight.If the Y con- tent≥0.1 wt-%,it occurs as solid solution state and is favorable to high temperature compressive properties and oxidation resistance of the alloy.While Y≥0.3 wt-%,the forma- tion of YNi_5 is predominant in the shape of irregular strips inside Ni_3Al grains and along their grain boundaries.This seems to be quite harmful to high temperature strength,ductility and oxidation resistance of the alloy.

Key words: Ni_3Al, YNi_5 phase, Y, compressive property, oxidation resistance