A Comparative Study of Microstructures and Mechanical Behavior of Laser Metal Deposited and Electron Beam Melted Ti-6Al-4V

The microstructures and mechanical properties of Ti-6Al-4V fabricated using laser metal deposition (LMD) and electron beam melting (EBM) were investigated and compared. The hardness, strength and work hardening exponent (n) of the LMD samples are superior to that of EBM samples. The EBM samples are more ductile, exhibit resistance to rapid plastic strain localization and have uniform hardness throughout the build. A detailed microstructural characterization was conducted for both alloys before and after the tensile tests. The differences in mechanical behavior of the two samples originate from their distinct dislocation densities within α and the relative proportions of Widmanstätten and colony type arrangements of the α+β laths, which in turn are an outcome of the distinct cooling profiles in the two additive manufacturing methods. On the basis of these results, strategies to improve the mechanical properties of both alloys are discussed.