Metallurgical Defects and Tensile Properties of a High Nb–TiAl Alloy Fabricated by Hot Isostatic Pressing of Prealloyed Powder

Hot isostatic pressing (HIP) of prealloyed powder has been consistently recognized as one highly promising near‐net‐shaping technique for difficult‐to‐form TiAl intermetallics. However, when HIP sintering the highly reactive TiAl prealloyed powders, obstinate prior particle boundaries (PPBs) are generated, critically compromising mechanical performance. This study systematically investigates the origin of PPBs and their influences on tensile properties of a high Nb–TiAl alloy fabricated by HIPing the prealloyed powder stored for a long term. It reveals that routine HIP of 1260 °C/165 MPa/3 h generates a fully dense and fine‐grained microstructure, but α 2 ‐grain‐dominant circular PPBs remain. Crucially, it is demonstrated that these PPBs originate from the oxygen‐enriched nanoscale oxide shells of powder precursors, which survive the α 2 ‐grains. The PPBs substantially lower the interfacial bonding strength and induce brittle fracture at room temperature (RT). Innovative near‐alpha forging is proposed to eliminate PPBs while tailoring a homogeneous, nearly fully lamellar microstructure. The wrought billet achieves exceptional tensile properties with ultimate tensile strength of 890 MPa at RT and 685 MPa at 800 °C, as well as acceptable RT elongation of 1.65%. This work provides fundamental insights into the formation mechanism of PPBs and establishes a microstructure design paradigm for high‐performance powder metallurgy TiAl alloys.