Effects of inclusions on dislocation behavior during deformation process of dissimilar steel-welded joints using acoustic emission and transmission electron microscopy

Dissimilar welded joints are widely used, and the research on their deformation mechanism is of great significance. Effects of inclusions on dislocation behavior during deformation process of dissimilar steel-welded joints were studied with the aid of acoustic emission (AE) and transmission electron microscope (TEM). In this study, Q345B base metal (BM), Q345B/Q345B (SW), and Q345B/Q235B (DM) welded joints were selected. The results show that the deformation mechanism of the DW sample during the yielding stage is dislocation unpinning, which is from synergistically acting of inclusions and coarse ferrite grains, which is different from the BM and SW samples. During the hardening stage, inclusions with diameter x (2 μm < x) and the proportion of inclusions with diameter x may be the two critical factors affecting the new Portevin Le Châtelier-like behavior at room temperature. Moreover, this paper proposes a characterization method based on AE and material microscopic damage.