Freeform fabrication of Ti–Ni and Ti–Fe intermetallic alloys by 3D Micro Welding

A novel freeform fabrication method for refractory metals named 3D Micro Welding (3DMW) has been proposed, which is a rapid prototyping combined with TIG (Tungsten Inert Gas) welding. Formation of beads and small pin objects composed of the Ti–Ni and Ti–Fe intermetallic alloy phases was attempted. Morphological changes of their beads in diameter, height, and contact angle were investigated as a function of the pulsed-arc peak current. As the arc peak current increased from 5 A to 30 A, the height and the contact angle decreased, while the bead diameter increased in Ti–Ni and Ti–Fe systems. Ti, Ti2Ni and TiNi phases were formed in the Ti–Ni system, while Ti, TiFe and TiFe2 phases in the Ti–Fe system. Small pin objects of these two systems were made by stacking molten beads on a fixed z-axis and their microstructures were observed. There were micro-cracks in beads of both system, but no crack appeared in these small pin objects.