Welding Metallurgy and Weldability of High Manganese Structural Damping Steels

Fe-Mn alloys have been identified as suitable candidates for structural applications that require damping. Damping is the ability of a material to convert mechanical vibrations into other forms of energy (usually heat), which is then dissipated in the material. Fe-Mn alloys do this by the oscillatory movement of various boundaries in their microstructure. Fabricating large structural damping components often requires fusion welding, so it is important that these alloys are weldable. The welding metallurgy and weldability of three high manganese steels were investigated using Varestraint testing, 3D heat flow and solidification modeling, electron probe microanalysis (EPMA), and scanning electron microscopy (SEM). The high manganese steels studied were found to have poor resistance to solidification cracking compared to existing weldable commercial alloys. Through heat flow and solidification modeling, it was established that the ranking of the alloys in the Varestraint test correlated to the size of the crack-susceptible solid + liquid region formed during welding. This was further investigated by tracking solute segregation behavior and its effects on secondary phase formation. Aggressive solute segregation and the concomitant formation of deleterious secondary phases degraded weldability in these alloys. Although it is useful for damping purposes, Si was found to be particularly detrimental to weldability in Fe-Mn systems.