· Ti₂AlNb — Ti-22Al-25Nb (O-phase based): Lightweight high-temperature intermetallic with tunable B2 + O + α₂ three-phase microstructure, the main candidate for the 600–750 °C range. Data are representative values for typical and rolled Ti-22Al-25Nb.

· TC4 — Ti-6Al-4V (α+β): The most common α+β titanium alloy. In the annealed condition σb ≥895 MPa with 10–15% elongation; long-term service limit is approximately 400°C.

· TC4-ELI — Grade 23, extra-low interstitial: Ultra-low interstitial version of TC4, used for implants and cryogenic service. Ductility and fracture toughness are better, but the high-temperature ceiling is lower.

· GH4169 — Inconel 718, Ni-based: The benchmark wrought Ni-based alloy. Below 650 °C its yield strength ranks first among wrought superalloys; long-term service range −253 to 650 °C.

· γ-TiAl — Ti-48Al-2Cr-2Nb: Lowest density at approximately 3.97 g/cm³; already in service in GEnx low-pressure turbine blades, but room-temperature ductility is often below 2% and the processing window is narrow.

· [600–750 °C / static hot section] Ti₂AlNb first choice: approximately 35–40% lighter than Ni-based alloys, with a B2 + O microstructure balancing strength and ductility. It is the preferred substitute for GH4169 in casings, heat shields, and seal rings.

· [Compressor rear / discs / blisks] Ti₂AlNb engineering billet (CITIC C-GA / Baoti) → isothermal forging + duplex heat treatment. If the stress exceeds the upper limit of the temperature window, step back to high-strength TC4 or move up to Ni-based alloys.

· [Main rotating parts / high-cycle fatigue] Ti₂AlNb is still in the validation phase, with less toughness reserve than GH4169; not the first choice for now. Ni-based turbine discs and blades are preferred.

· [Low-pressure turbine / blades / castings] γ-TiAl (Ti-48Al-2Cr-2Nb, etc.) is already in service with even lower density (approximately 3.97 g/cm³), but its room-temperature ductility is poor and the processing window is narrow.

· [≤ 400 °C / general load-bearing] TC4 offers the best cost-performance and process maturity; there is no need to use Ti₂AlNb. Ti-6Al-4V ELI is used for implants and cryogenic service.

· [Welded integrated /hot-section structure] Ti₂AlNb requires vacuum electron-beam welding / diffusion bonding plus post-weld aging, which is more difficult than GH4169. For welded parts, Ni-based alloys are preferred.

· [Additive near-net / complex thin-wall] Ti₂AlNb is well suited to LPBF; rapid solidification actually favours a fine-grained heterogeneous microstructure, making it an ideal route for heterostructure design.

· [Cost-sensitive / batch parts] Ti₂AlNb is a high-performance specialty material with high unit cost, a narrow heat-treatment window, and a steep yield curve; it is not suitable as a general substitute.