Microstructure Characterization of Laser Welded near-β titanium Alloy 'TLM' under Different Process Conditions

The microstructures of laser welds of the near-β titanium alloy TLM were studied for substrates in the as hot rolled, solution treated and solution treated and aged conditions. Irrespective of substrate condition the fusion zone consists of a cellular β structure. Trends in bulk hardness of the various conditions seem to be carried through into the weld consistently across the profile. The hardness in the fusion zone remained similar to that of the bulk. However, a drop in hardness occurs in the HAZ. Lath that formed around the hardness indent of the fusion zone and HAZ suggest that the weld undergoes a martensitic transformation to α" during deformation.