Study on Microstructure and Mechanical Properties of TA15 Titanium Alloy Repaired by Laser Deposition Under Various Annealing Processes

Abstract

Laser deposition repair technology is a process that utilizes light and heat to locally melt the material on the surface of an alloy, enabling the repair of the material. The alloy produced by this method exhibits significant differences compared to those obtained through conventional forging techniques. Consequently, selecting the appropriate heat treatment process is critical for optimizing the mechanical properties of the repaired alloy. This study investigates the grain morphology, microstructure, and mechanical properties of TA15 titanium alloy repaired via laser deposition, under various annealing conditions, both at room temperature and elevated temperatures. The results indicate that specimens annealed below the β-phase transition temperature exhibit a bimodal microstructure in the base material region. The heat-affected zone (HAZ) is characterized by a mixture of “sawtooth” α-phase, lamellar α-phase, and β-phase, while the repaired region exhibits a net-basket-like microstructure. For the specimen annealed at 1000 °C for 2 h, the α-phase in the base material region is completely eliminated, whereas in the HAZ, the α-phase predominantly exists in the form of cluster bundles. Polygonal grains are observed in the repaired zone. The HTR900-annealed specimen demonstrates a favorable balance between strength and ductility at room temperature, exhibiting a tensile strength of 971.86 MPa, a yield strength of 791.68 MPa, and an elongation of 13.23%. At 500 °C, the HTH900-annealed specimen maintains a satisfactory combination of strength and plasticity. Under elevated temperature conditions (500 °C), the mechanical properties of both HTH900 and HTH950 annealed specimens outperform those of the HTH1000 annealed specimens.