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Ambient and High-Temperature Bulk Characterization of Additively Manufactured Ti-6Al-4V Using Neutron Diffraction

ABSTRACT

              Characterization of the bulk microstructure using neutron diffraction has been applied to investigate the phase fractions and textures of α- and β-phases in Ti-6Al-4V fabricated by additive manufacturing. The microstructure of a specimen cut from a fan structure, built by either electron beam melting (EBM) or selective laser melting, indicated that predominantly the build direction and not the fan angle determines the microstructure. In situ heating experiments of specimens from a rod built using EBM provided insight into the lattice strain, phase fraction, and texture evolution, providing a rich picture of the microstructure changes during heat treatment of additively manufactured Ti-6Al-4V. A remarkably low weight fraction of β-phase at lower temperatures, deviations from thermal expansion behavior attributed to vanadium repartitioning, as well as texture strengthening were observed.