Effect of titanium–boron additions on grain refinement of AA 2219 gas tungsten arc welds

Abstract

Grain refinement of aluminium weld metal involves the transition from coarse columnar grains to smaller, more equiaxed grains (sometimes referred to as columnar to equiaxed transition). This refinement in grain size and shape results in both improved mechanical properties (ductility and toughness) and significant improvement in weldability. The present study has investigated the influence of Tibor additions on the structure and mechanical properties of AA 2219 gas tungsten arc (GTA) weldments. Controlled amounts of Tibor grain refiner (containing Ti and B in a ratio of 5∶1) were introduced into the molten pool of AA 2219 by predeposited cast inserts under different welding conditions by GTA welding. Full penetration GTA welds were prepared using alternating current. It was observed that grain size was decreased with increasing amounts of Tibor. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength and ductility. It is also found that welds subjected to post-weld aging treatment displayed superior mechanical properties.