Twin and twin intersection phenomena in a creep deformed microalloyed directionally solidified high Nb containing TiAl alloy

•The combination of directional solidification and microalloying can significantly refine the columnar grains and homogenize the microstructure of TiAl alloy.•Compared with ternary TiAl alloy, the microalloying high-Nb TiAl alloy exhibits more superior creep property at 760 °C/275 MPa.•The decrease of stacking fault energy can promote the dislocation dissociation and the formation of deformation nanotwins.•Twin intersections will create more boundaries in the lamellar matrix, which will act as obstacles to dislocation movement.