Integrated manufacturing method for compressor blisks: LDED Ti65 on sheet Ti-6Al-4V

Abstract

This research focuses on the integrated manufacturing technology of aero-engine compressor blisks, especially the deposition of Ti65 powder on a Ti-6Al-4V substrate using laser direct energy deposition (LDED). The microstructure, microhardness, and tensile properties of the samples were investigated. The analysis revealed that the microstructure of the specimens can be divided into LDED-Ti65, heat-affected zone (HAZ), and Ti-6Al-4V substrate. The microstructure of Ti65 exhibited different morphologies of α laths. Ti-6 A l-4V presented a bimodal microstructure. The HAZ formed a gradient microstructure comprising lamellar α, α laths, as well as residual β-transformed (β_t) structure and primary α (α_p). The HAZ's lowest microhardness (339 HV) was attributed to the cyclic thermal effects during deposition, which dissolved α_p and secondary α (α_s). The ultimate tensile strength (UTS) and yield strength (YS) of the HAZ specimens were 1005 ± 10 MPa and 910 ± 8 MPa, respectively, with a maximum elongation (δ) of 11.5 ± 0.5 %. The excellent ductility was attributed to angular grain boundary ratios and finer α adjustment. Using the digital image correlation (DIC) technique, stress concentration and inhomogeneous deformation were observed to occur first in the HAZ. The inhomogeneity of plastic strain was microstructure-dependent. Loading-unloading-reloading tests (LUR) showed that strain hardening induced by the gradient microstructure of the HAZ during plastic deformation enhanced the ductility of the specimen through a synergistic effect.