DED-LB manufactured Ti–6Al–4V–4Cu alloy: materials development, characterization, and in vivo biocompatibility

This study investigates the fabrication, characterization and biocompatibility of a Ti–6Al–4V–4Cu alloy produced from spherical Ti–6Al–4V and Cu powders using the directed energy deposition (DED-LB) process with an annular laser beam (ALB). Based on process stability related wall rectangularity, and interlayer bonding, the optimal build strategy of the wall samples was achieved by a bi-directional path with reducing ALB power and initial power of 1250 W. Microstructural characterization included optical microscopy for grain morphology, SEM with analysis for microstructure and elemental distribution, and XRD for phase identification. Electrochemical performance was assessed in a simulated physiological environment, demonstrating passive behavior and corrosion resistance. To evaluate in vivo biocompatibility, disc-shaped implants were inserted subcutaneously in mice and monitored for physiological, hematological, biochemical, and histological responses over a 56-day period. Mice exhibited no signs of adverse effects with stable feed and water intake, normal body weight, and typical behavior. Hematological and metabolic profiles revealed no significant differences between the Ti–6Al–4V–4Cu, Ti–6Al–4V, sham, and untreated groups. Histological analysis revealed that the implants were well-integrated with surrounding tissues, with no evidence of granulomatous inflammation, immune cell infiltration, or abnormal tissue morphology. ICP-MS analysis of the mouse serum revealed stable concentrations of Cu, Al, V, and Ti, indicating no systemic metal release. These findings confirm that DED-LB fabricated Ti–6Al–4V–4Cu alloy exhibits favorable in vivo biocompatibility and systemic safety in mice. The results support its potential for biomedical applications that require corrosion resistance and biocompatibility, and warrant further in vivo evaluation of its antibacterial properties.