A novel hybrid joining strategy for Ti/steel dissimilar metals: Laser pre-melting interlayer modification assisted CMT welding

• Laser pre-melting V/CNTs interlayer/CMT composite process significantly eliminates interfacial cracks and porosity defects. • This innovative process achieves a grain refinement rate of 35.7% in the weld seam. • The joint tensile strength increases by 37.1% and average hardness improves by 9.71%, attributed to fine-grain strengthening and second-phase strengthening mechanisms. • This process regulates the in-situ generated nanoscale TiC, VC, and CuTi₂ strengthening phases, promoting equiaxed grain formation and driving the Orowan strengthening effect.