Response surface approach to optimize the pulsed current gas tungsten arc welding parameters of Ti?6Al?4V titanium alloy

Titanium alloy (Ti−6Al-−4V) is very widely used in the fabrication of advanced industrial equipment, combat vehicles, gas turbines, spacecraft and so on. The preferred welding process for titanium alloy is gas tungsten arc (GTA) welding due to its comparatively easier applicability and better economy. However, welding of titanium alloy leads to grain coarsening at the fusion zone and the heat-affected zone, and this often results in inferior weld mechanical properties and poor resistance to hot cracking. Hence, in this investigation an attempt has been made to refine the fusion zone microstructure of titanium alloy by using a pulsed current GTA welding process instead of a constant current GTA welding process. Further mathematical models were developed by means of a response surface method, which enabled the process parameters to be optimized to achieve a minimum grain size and maximum hardness in GTA welding of the alloy under study. The parameter optimization involved the use of a response surface, contour plots and Kuhn-Tucker conditions.