Enhancing high-temperature creep resistance of additively manufactured Ti2AlNb alloys via vacuum hot isostatic pressing-induced tailoring of coherent interfaces

This study investigates the microstructural evolution and creep behavior of additively manufactured Ti-22Al-25Nb intermetallic alloys under different post-processing conditions. Selective laser melting (SLM) was employed to fabricate samples, followed by two distinct heat treatments (HT1: 990°C-1h with water quenching + 800°C-2h with air cooling; HT2: hot isostatic pressing at 1200 °C/150 MPa + aging). Microstructural characterization revealed that the HT1-treated sample exhibited a semi-coherent B2/O interface structure with submicron pores and localized compositional segregation, resulting in interfacial dislocation pile-ups and stress concentrations. In contrast, the HIP-treated HT2 counterpart demonstrated fully coherent B2/O interfaces with negligible lattice mismatch (Δa/a <2 %) in a eutectic-like multi-phase configuration combining coarse O-phase plates and a refined B2 matrix, eliminating porosity and homogenizing phase distribution. Creep tests at 650 °C/150 MPa showed that the HT2 sample achieved a minimum creep rate of 6 × 10⁻⁵ h⁻¹, nearly three times lower than the HT1 one (1.7 × 10⁻⁴ h⁻¹) at identical conditions, due to the coherent interface-mediated dislocation glide and the suppressed cavity nucleation. The study highlights the critical role of interfacial coherency and defect elimination in enhancing high-temperature creep resistance, providing a microstructure-guided strategy for optimizing additively manufactured Ti₂AlNb alloys for aerospace applications.