New transformation mechanism of TiB from B f to B27 structure in β-solidified TiAl alloys

Both transformations of structure and morphology occur on the borides formed in β-solidified TiAl alloys during heat treatment at 1300℃. Flake-like TiB(Bf) transforms to blocky TiB(B27). Two types of planar faults in Bf occur during transformation, respectively on (010) and {110) plane. Displacement on {110) Bf directly realizes the transformation, and the driving force originates from the shear stress caused by the lattice distortion of a new (Ti, Al, B) structure. This new structure is generated because Al atoms occupy the interstitial sites in a three-layer structure formed due to the stacking faults on (010) Bf.