Single-composition functionally graded Ti-6Al-4 V for mimicking composite material fiber reinforcement through post-heating laser scanning

Process-induced microstructure modification was investigated for the strengthening mechanism of laser powder bed fusion fabricated (LPBF) Ti-6Al-4 V material. An innovative approach by mimicking the fiber structure of the composite materials was studied. Different cylindrical reinforcement diameters were selected in the LPBF-fabricated Ti-6Al-4 V samples to replicate the function of the carbon fibers in composite materials, providing stiffness and reinforcement in the matrix. The corresponding regions of the assigned reinforcement shape at each layer were exposed to a secondary laser scan through the sample during the fabrication. Multi-scan laser scanning strategies, involving a combination of laser power and scan speed, were employed after the melting laser scan to maximize the relative density of the material. The optimized post-heating laser scan enhanced the relative density (> 99.95%), recrystallized the α and α′ phases’ lath morphology, modified the lattice structure, transformed the initial microstrain mode, and enhanced the inherent grain texture of the PBF fabricated Ti-6Al-4 V. The tailored microstructure achieved a 46.5% higher yield strength (YS) accompanied by a 99.3% higher elongation.