Influence of low transformation temperature (LTT) welding consumable on microstructure and deformation behavior of welded joint

Low transformation temperature (LTT) welding consumables significantly influence mechanical properties. This work investigates the effect of LTT welding consumables on the microstructure and tensile deformation behavior of welded joints. The results show that, compared with conventional joint (C joint), LTT joint exhibits comparable strength but superior ductility. The elongation of the LTT joint (10.5%) is approximately 50% higher than that of the C joint (7%). In both joints, the weld zone exhibits the highest microhardness, while the outer heat affected zone (OHAZ) shows the lowest, promoting strain localization. Compared with the C joint, the OHAZ in the LTT joint contains a lower volume fraction of ferrite, resulting in a smaller microhardness difference between the weld zone and OHAZ. This reduced hardness difference reduces strain localization and enhances the ductility. Furthermore, stress concentrations caused by dislocation pile-up at grain boundaries in the OHAZ are likely the primary cause of failure in both joint types.