Metallurgical and mechanical characterization of mild steel-mild steel joint formed by microwave hybrid heating process

In this paper, mild steel-mild steel (MS-MS) joints fabricated through microwave hybrid heating (MHH) have been characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), electron probe micro analyser (EPMA), Vicker's microhardness measurement and tensile strength. The XRD spectrum of the developed joints shows substitution type of solid solution form in the joint zone. The back scattered electron (BSE) images of the joint obtained by SEM show complete melting of powder particle and consequently diffusion bonding takes place between the substrate and the powder particle. The electron probe micro analysis shows diffusion of element across the joint. The Vicker's micro hardness of the joints was measured to be 420 +/- 30 Hv, which is higher than that of substrate hardness 230 +/- 10 Hv. The tensile strength of the sample was measured by an universal testing machine and found to be 240 MPa which is about 50% of base material strength. The SEM micrographs of the fractured sample indicate mixed modes of failure during fracture of the joint; both ductile and brittle modes of failures occurred as indicated by dimple and cleavage of the brittle faces, respectively.