Microstructure and interfacial reactions in the bonding zone of explosively welded Zr700 and carbon steel plates

The microstructure of an explosive cladding joint formed between parallel Zr700 alloy and carbon steel plates was examined with the use of scanning and transmission electron microscopes equipped with energy dispersive spectrometry. The study focused on near-the-interface microstructural changes and possible interdiffusion between the plates. At the macro-scale, the interfaces were outlined by a characteristic sharp transition, indicating that there was no mechanical mixing between the welded metals in the solid state. At the micro-scale, the melted zones often showed non-uniform swirl-like areas of a similar contrast. The nano-scale analysis revealed that the melted areas were composed of mixed amorphous and nano-crystalline phases. The bonding was always achieved by way of surface melting of the joined materials, which might be invisible for observation methods other than transmission electron microscopy.