Microstructural characteristics and mechanical properties of rotary friction-welded dissimilar AISI 431 steel/AISI 1018 steel joints

The main objective of this study was to analyze the microstructural characteristics and strength performance of dissimilar AISI 431 steel/AISI 1018 steel joints developed using rotary friction welding. The microstructural characteristics of different regions of dissimilar rod-to-plate joints were analyzed using optical microscopy. The tensile properties and microhardness of dissimilar rod-to-plate joints were evaluated to assess the joint performance. The microhardness distribution across the cross-sectional region of dissimilar rod-to-plate joints was recorded and correlated with the tensile failure. Scanning electron microscopy was used to analyze the fractured region of dissimilar rod-to-plate tensile specimens. Results showed that the dissimilar AISI 431 steel/AISI 1018 steel joints steel exhibited a tensile strength of 650 MPa, a yield strength of 452 MPa, and a % elongation of 18%. The microhardness of the weld interface (WI) was higher up to 515 HV0.5. The grain growth and resulting lower hardness in heat-affected zone (HAZ) are mainly responsible for the failure of the joints in HAZ only. The superior tensile properties and greater interface hardness of dissimilar AISI 431 steel/AISI 1018 steel joints are correlated with the evolution of finer grain microstructure in the WI zone.