Method for obtaining tri-state structure during titanium alloy local loading formation

The invention discloses a method for obtaining a tri-state structure during titanium alloy local loading formation, comprising the following steps of: performing improved forging on a billet, pre-forming, performing local loading formation by using a partitioning mould, finishing and thermally treating to obtain a formed forged piece, and obtaining the tri-state structure by controlling parameters for the local loading formation. In the invention, the forged piece is kept at a nearly beta forging temperature and deformed; the content of equiaxed alpha is controlled within a proper range; then, the forged piece is kept at a normal forging temperature and deformed so as to generate strip alpha in a certain proportion; and the deformation amount of each pass can be controlled within a proper range by adjusting and controlling a loading pass so as to prevent the strip alpha from being spheroidized greatly. According to the invention, the tri-state structure composed of the equiaxed alpha, the strip alpha and a beta transformation matrix can be obtained from different regions of the forged piece; structure forms in different deformation regions and contents of various phases are similar; the obtained tri-state structure integrates the advantages of a bi-state structure and a slice layer structure and has good comprehensive performance; and the plasticity, the heat stability, the high-temperature performance and the fracture toughness of the tri-state structure are better.