What are the challenges in welding dissimilar materials and how do you address them?

Dissimilar welding challenges include: Difference in melting points (controls dilution and joint geometry), Thermal expansion mismatch (causes residual stress and cracking), Intermetallic compound formation (brittle phases at interface - Fe-Al, Ti-Al systems), Galvanic corrosion potential, and Carbon migration in ferritic-austenitic joints. Solutions: Filler metal selection (nickel-based for many combinations, butter layers), Process selection (low heat input - laser, electron beam, FSW), Joint design optimization (transition pieces, interlayers), Controlled dilution through weld parameters, Post-weld heat treatment (stress relief, diffusion control), and Coating/cladding alternatives. Examples: Steel to aluminum requires mechanical joining or explosive welding; stainless to carbon steel uses ENiCrFe-3 filler.