The characteristics of macro-and microstructure of cast Ti-46Al-xHf-yB （x=0

3

5

7; y=0

0.2

0.6

1.0） alloys were observed to understand the coupling effects of hafnium and boron additions on the solidification structure evolution in the Ti-46Al alloy. The results reveal that with increasing in Hf and B contents

structure morphology of the alloy is converted from coarse columnar to fine columnar dendrite

then to equiaxed dendrite and further to fine near granular grain. Hafnium content can promote the formation of TiB

2

particles

resulting in the motion-down of β-Ti/TiB

2

eutectic line. With Hf content less than 7%

microstructure of the alloy is composed of primary β phase and eutectic phase TiB

2

with ribbon-like shape mainly existing in the interdendrite

while with 7%Hf and 1% B content

primary phase TiB

2

with needle-like shape existing in near granular grain center can be observed in the microstructure.