Freeform fabrication of titanium metal and intermetallic alloys by three-dimensional micro welding

3D micro welding (3DMW) is a new freeform, fabrication method which combines tungsten inert gas (TIG) welding, rapid prototyping (RP), and self-propagating high temperature synthesis (SHS). The optimization of forming parameters such as arc peak current, bead diameter and contact angle was investigated. As the arc peak current increased, the height and the contact angle of a titanium bead were decreased, but the width increased. 3D titanium pins with needle-like dendritic microstructure of alpha-phase titanium were formed by continuous stacking and welding of titanium beads. Simple intermetallic alloy pin objects of Ni-Al, Ti-Ni and Ti-Fe systems were also formed by alternate stacking of their component wires. No pore and crack was observed but the uniform composition was observed. The exothermic SHS reactions should take place and assist the intermetallic alloy formation. 3D titanium objects of ring and double helix shapes were formed directly from their computer models without using molds or dies. (c) 2006 Elsevier Ltd. All rights reserved.