Wire‐Laser‐Directed Energy Deposition of Ti‐6Al‐4V Alloy Under Vacuum: Effect of Substrate Preheating on the Refinement of Prior‐β Grain Structure

The effect of stress relieving and substrate preheating on the grain refinement of additively manufactured Ti‐6Al‐4V at room and elevated temperatures is investigated. Specimens are produced using wire‐based directed energy deposition under vacuum conditions. The microstructure is characterized by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X‐ray diffraction (XRD). Tensile tests are conducted at room temperature and at 700 °C. The as‐deposited specimens exhibit a heterogeneous microstructure consisting of fine acicular α′‐martensite and fine Widmanstätten structures. Substrate preheating at 600 °C enables a complete transition from a columnar grain structure in the as‐deposited condition to a refined prior‐β grain structure. The as‐substrate‐heated specimens show the highest tensile strength of 1010 MPa with 3% elongation at room temperature and 600 MPa with 15% elongation at 700 °C.