Production and characterization of AlN and Al₂O₃ reinforced Ti–6Al–4V alloy via spark plasma sintering method

The Ti–6Al–4V alloy is widely utilized in aerospace and structural applications, especially in the fabrication of turbine engine components, owing to its superior strength-to-weight ratio and excellent corrosion resistance. In this study, Ti–6Al–4V alloys reinforced with 1, 2, and 3 wt% AlN (aluminium nitride) and Al₂O₃ (alumina) were fabricated by spark plasma sintering (SPS) under argon atmosphere, and their structural, mechanical, and tribological properties were systematically investigated with aim of enhancing its hardness and wear resistance. The addition of AlN and Al₂O₃ disrupted the Widmanstätten lamellar structure, leading to the formation of a bimodal (duplex) microstructure that improved densification behavior and contributed to higher hardness and compressive strength. Particularly, 3 wt% AlN refined the microstructure and impeded grain coarsening, resulting in the highest hardness (524.1 HV) and compressive strength (2047 MPa). AlN primarily strengthened the alloy through α-phase stabilization, grain refinement, and dispersion hardening, whereas Al₂O₃ induced continuous grain size reduction, enhancing hardness and wear resistance by increasing grain boundary density and restricting dislocation motion. Overall, the study demonstrates that low levels of ceramic reinforcement can significantly improve the performance of Ti–6Al–4V alloys through combined densification, microstructural refinement, and dispersion strengthening mechanisms.