Microstructure and Hardness of Ti-6242 Alloy Fabricated by Electron Beam Powder Bed Fusion and Laser Powder Bed Fusion Methods

Introduction and Objectives: Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy is a near-alpha titanium alloy widely used in biomedical, automobile, and aviation industries, known for having a high service temperature. The objectives of this study are to compare the electron beam melting and selected laser melting techniques in terms of the microstructure and hardness developed in Ti6242 alloy.Materials and Methods: Microstructure and hardness of Ti6242 alloy samples produced by the two-powder bed fusion techniques were analyzed using optical and scanning electron microscopy, X-ray diffractometry, and Vickers hardness test.Results: The porosity levels in both samples were within the acceptable ranges for powder bed fusion processes. The solidified microstructure of laser powder bed fusion samples consisted of columnar β grains with martensitic α' phase, and that of electron beam powder bed fusion sample consisted of lamellar α+β phases with Widmanstätten and basketweave morphology and α colonies. Williamson-Hall plots revealed higher lattice microstrain in the laser powder bed fusion process. The average hardness values of electron beam powder bed fusion and laser powder bed fusion samples were approximately 408 HV and 401 HV.Conclusion: Both powder bed fusion techniques employed were capable of producing samples of acceptable porosity levels. The solidified microstructures of the two techniques were somewhat different due to different heating and cooling histories experienced. The electron beam powder bed fusion sample enjoyed smaller lattice microstrain and higher hardness than the laser beam powder bed fusion sample. Hardness of both samples was higher than those of the conventionally fabricated components.