To investigate the effect of Si addition on the solidification structure

the alloys with nominal compositions of Ti-46Al-5Hf-0.6BxSi(x=0

0.5%

1.5%

3%)are arc-melted into small ingots in an argon atmosphere.The characteristics of macro and micro structures are studied using OM

SEM and XRD techniques.The results show that Si addition forms Ti5Si3 phase in the alloy.When Si=0.5

1.5 and 3.0

the solidification structure is near lamellar with coarse columnar dendrite morphology

fine columnar dendrite and equiaxed...