HAZ Characterization and Mechanical Properties of QP980-DP980 Laser Welded Joints

Abstract The QP980-DP980 dissimilar steel joints were fabricated by fiber laser welding. weld zone (WZ) was fully martensitic structure, and heat-affected (HAZ) contained newly-formed martensite partially tempered (TM) in both steels. super-critical HAZ of the QP980 side had higher microhardness (~ 549.5 Hv) than that WZ due to finer martensite. A softened present DP980, dropped DP980 ? 21.8 Hv 40.9 Hv, respectively. Dislocation walls slip bands likely formed at grain boundaries with increase strain, leading formation low angle (LAGBs). accumulation more easily occurred LAGBs HAGBs, which led significant dislocation interaction cracks. electron back-scattered diffraction (EBSD) results showed fraction sub-critical highest under different deformation conditions during tensile testing, resulting failure located side. presented elongation 11.21%) ultimate strength 1011.53 MPa) DP980-DP980 similar joints, because process joint 8.2% 991.38 MPa), strain concentration firstly on excellent BM. Moreover, Erichsen cupping tests welded lowest value 5.92 mm) peak punch force 28.4 kN) presence large amount brittle inhomogeneous deformation.