Currently, a gap in understanding the mechanism of interlayer explosives exists. This study systematically investigated this mechanism using TP 270C/SUS 821L1 to fill this knowledge gap. By comparing the outcomes of direct and interlayer welding through methods such as optical microscope (OM), computed tomography (CT), electron probe micro-analysis (EPMA), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), nanoindentation, and tensile shear test, it was found that an interlayer can significantly lessen the energy at the target interface. This was further evident when comparing welds with varying interlayer thicknesses, showing that thinner interlayers lead to less energy transfer between the flying plate and the interlayers. Notably, at an interlayer thickness of 0.1 mm, the welding interface appeared irregular. The smoothed particle hydrodynamics (SPH) method was employed to simulate the welding, highlighting the interlayer's impact on factors like pressure, jet, temperature, and melting. This simulation also explained why the 0.1 mm interlayer had an irregular interface due to jetting affecting the welding between the flyer plate and interlayer. The study also analyzed the weldability window in interlayer explosive welding, noting how the interlayer influenced its upper and lower limits. The relation between interlayer thickness and the constant k in the lower limit was examined, along with the minimum velocity needed for the flyer plate to generate a jet VP. Their relationship satisfied exponential functions in the detonation velocity range of 1800–3000 m/s. This study thus established a link between traditional and interlayer explosive welding.
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