On the effect of the thermal cycle during the directed energy deposition application to the in-situ production of a Ti-Mo alloy functionally graded structure

Abstract

In this work, almost dense (over 99.8 %) Ti-Mo alloy samples were manufactured by directed energy deposition (DED) from a mixture of pure Ti and pure Mo (7.5 wt.%) powders. As a consequence of thermal accumulation and in-situ heat treating during the DED process, as-deposited samples present a graded microstructure along the building direction along with a phase transition from hcp-α Ti to bbc-β Ti. Mechanical properties were determined by tensile tests from flat samples harvested at different altitude positions. As altitude increases from the base plate, yield strength decreases from 681 MPa to 579 MPa and ultimate tensile strength from 791 MPa to 686 MPa. Elongation of the as-deposited material increases from 10 % to 25 % while the Young’s modulus keeps a low value of 105 GPa for the entire DEDed sample.