Densification, microstructural characterization, and the electrochemical behaviour of spark-plasma sintered Ti6Al4V-5Cr-TiB₂ composites

The impacts of Cr-TiB₂ addition on densification, hardness, microstructure, phase transformation, and corrosion were examined. The results indicated an even and uniform dispersion of TiB₂ particles in the titanium matrix, with no noticeable interfaces throughout the sintering process. The relative density of the sintered titanium-based composites dropped, with an increase in TiB₂ percentage. The microhardness result indicated that Ti6Al4V has 326 HV_0.5, while the maximum hardness was 598 HV_0.5, produced from 20 wt.% TiB₂ ceramic particles. The Ti6Al4V alloy depicts α-phase forms parallel plates in the prior β-grain borders and expands into the β-grain to create α-colonies, while the addition of 5–20 wt.% Cr-TiB₂ resulted in a microstructural transformation characterized by equiaxed α-precipitates embedded within the β-phase matrix, for all samples. The electrochemical behaviour revealed that the E_corr decreased as TiB₂ increased, while the i_corr was higher. However, samples containing 5Cr and 5Cr-5TiB₂ moved to a more positive E_corr region, whereas the i_corr altered to a more negative area. This meant that the presence of ceramic reinforcements increased the corrosion resistance of the alloys and that higher concentrations of titanium diboride provided less protection against ion attack in a chloride environment.