Fine Structure Characterization of Explosively Welded GH3535/316H Bimetallic Plate Interface

To provide one more cost-effective structural materials for the ultra-high temperature molten salt thermal storage systems, the explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates in the present work. The microstructures of the bonding interfaces have been extensively investigated by scanning electron microscope, energy dispersive spectrometer, and electron probe micro-analyzer. It was discovered that the bonding interfaces possess the periodic wavy morphology and are adorned by peninsula- or island-like transition zones. At higher magnification, matrix recrystallization region, fine grain region, columnar grain region, equiaxed grain region, and shrinkage porosity can be observed in the transition zones and the surrounding area. The analysis of electron backscattered diffraction demonstrated that the strain in the recrystallization region of the GH3535 matrix and transition zone is lower than the substrate. Strain concentration occurred at the interface and the solidification defects in the transition zone. The dislocation substructure in 316H near the interface was characterized by the electron channeling contrast imaging. The results showed that a lot of dislocations network was formed in the grains of 316H. Microhardness tests showed that the micro-hardness decreased as the distance from the welding interface increased, and the lowest hardness value was inside the transition zone.