Spark plasma sintering and structural evolution of HEAs-reinforced TiAl matrix composites

Abstract

This work demonstrates a novel approach for tailoring the phase architecture and mechanical response of TiAl intermetallics through high-entropy alloy (HEA) particle reinforcement combined with spark plasma sintering (SPS). The TiAl matrix retained a stable γ-TiAl + α₂-Ti 3 Al lamellar structure across the sintering range (850–950 °C), while the FCC HEA phase remained finely dispersed at 850–900 °C and developed detectable FCC HEA reflections at 950 °C, consistent with an HEA-rich FCC solid solution phase retained after SPS, and forming a γ + α₂ + FCC multiphase architecture. Increasing sintering temperature significantly improved densification and mechanical performance, achieving ∼99 ± 0.04% relative density, ∼351 ± 14.2 HV microhardness, ∼702 ± 7 MPa flexural strength, and ∼560 ± 7 MPa tensile strength, with fracture strain increasing to ∼1.6%. These improvements are associated with reduced porosity, enhanced lamellar continuity, improved matrix-reinforcement bonding, and the presence of FCC HEA domains that may assist local strain accommodation. Overall, the study demonstrates that SPS-assisted phase and microstructural engineering enable a synergistic strength-ductility response in HEA-reinforced TiAl composites, highlighting their potential as lightweight high-temperature structural materials for turbine and aerospace applications.