Directional solidification of TiAl alloys for aligning lamellar microstructures and mechanical properties of directionally-solidified ingots

The TiAl/Ti3Al lamellar structure has been successfully aligned parallel to the growth direction through directional solidification of TiAl ingots containing various alloying elements (Nb, Mo, Ta, W, Re, Si and so on) on the basis of the recently proposed method to predict the appropriate compositions by using an appropriately oriented seed from the TiAl-Si system (Ti-43Al-3Si). Here, we review the prediction method of alloy compositions appropriate for aligning the lamellar structure, the directional solidification (DS) processes and the mechanical properties of these DS ingots. These DS ingots with the lamellar structure all aligned parallel to the loading axis exhibit a very nice balance of mechanical properties such as yield strength, tensile ductility and creep properties, leading to a possibility of alloy design of high property level.