Ultrahigh cooling rates at the interface of explosively welded materials and their effect on the formation of the structure of mixing zones

Explosively welded metal plates are characterized by the formation of local microvolumes at the interlayer boundaries within which there is a mixing of interacting materials. These microvolumes can be located discretely along wavy boundaries or continuously in the form of thin interlayers along planar boundaries. Based on the results of many published works, it has been shown that the material in these zones is melted, and its subsequent solidification occurs at a high rate leading to the formation of metastable phases. In this paper, the formation of metastable phases in steel-steel, $\mathrm{Ta}$-steel, $\mathrm{Nb}$–$\mathrm{Al}$, and $\mathrm{Zr}$–$\mathrm{Cu}$ joints is analyzed. The cooling rates of these materials in mixing zones is estimated. Calculations show that the cooling rate of the melts formed in the welded zones of the investigated composites is in the range $10^3-10^6$ K/s. Cooling of mixing zones at such high rates results in the formation of metastable structures. In some cases, the crystallization of materials is suppressed and metallic glasses and quasicrystalline phases are formed in the melt zones.