Metallurgical characterisation of mild steel pipes joined using a multiparameter microwave heating process

The present investigation focuses on the metallurgical characterisation and process optimisation of mild steel pipes subjected to selective microwave hybrid heating (SMHH). Experiments were conducted at power levels of 700 and 900 W, considering power output and environmental conditions as the primary process parameters. Electron backscattered diffraction (EBSD) analysis revealed the formation of fine and mixed crystallographic plane distributions when processed at 700 W under an inert atmosphere, which resulted in higher kernel average misorientation (KAM) values, indicating increased localised plastic deformation and microstructural refinement. GOS mapping reveals a higher fraction of deformed grains in the joint processed at 700 W (inert atmosphere), leading to enhanced microstructural strengthening and superior hardness (283 ± 2.86 HV) relative to other processing parameters.