Effect of titanium content on weld microstructure and mechanical properties of bainitic GMA welds

Abstract

The effects of titanium content on the weld microstructure, mechanical properties, and inclusion characteristics were investigated in the as-deposited bainitic GMA weld metals having nearly constant level of oxygen content. It was found that titanium addition enhanced the formation of acicular ferrite with the maximum proportion being obtained at similar to 0.07 wt% Ti. The resultant change in weld microstructure with titanium content was well reflected in the Charpy impact toughness showing the lowest ductile-brittle transition temperature at 0.07 wt% Ti. Detailed TEM and STEM analysis preformed on weld metal inclusions demonstrated that the maximum acicular ferrite recorded in this weld is mainly attributable to the formation of manganese-depleted zone (MDZ) associating with the formation of nonmetallic inclusions dominant with Ti2O3 phase.