Effect of current pulses on the temperature distribution and microstructure in TIG tantalum welds

Abstract

The welding process employed for bonding metals by melting and solidification produces a joint which is generally inhomogeneous. The micro structure of the fused zone and its adjacent heat affected zone, HAZ, is usually different from the microstructure of the parent metal, obtained by mechanical working or heat treatment. The fused zone is usually composed of coarse columnar grains characteristic of as-cast structures. If the parent metal was originally cold-worked, recrystallization will occur in the HAZ, producing a coarse grained structure. As a result of the effect of the microstructure on the mechanical properties of the weld, the obtained joint may be weaker than the rest of the structure which was not affected by the heat of the welding. Although in some cases it is possible to improve the properties of the weld by post-welding heat treatment, different methods are tried in order to improve the microstructure directly during the welding process.