The microstructure and mechanical behaviors of the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy produced by laser melting deposition

The microstructure and mechanical properties of the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy produced by laser melting deposition have been investigated. The columnar grains of the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy due to the layer-by-layer epitaxial growth from the underlying template grains during laser melting deposition, which is roughly parallel to the deposition direction, had been found by optical microscopy; strong 10_1¯2α crystallographic texture has been confirmed by X-ray diffraction and electron backscattered diffraction. Depending on the last heating history, the microstructure of the alloy undergoes a continued change opposite to the deposition direction: martensitic α′ (transformed β); coarsened primary α laths with transformed β; coarsened primary α laths; and the fine basketweave microstructure with a few coarsened α laths or annealed martensitic α′. The average Vickers micro-hardness value of the alloy is 364 HV. The alloy parallel to the deposition direction presents lower tensile strength (925 MPa) and better elongation (18.8%), compared with 1025 MPa and 8.2% of that vertical to the deposition direction, which has been discussed using its microstructure characterization.m