Rapid Molding Mechanism of Melt-cast Explosive Based on High-pressure Subcooling

The rapid molding of melt-cast explosive can be achieved under high-pressure subcooling conditions, but the underlying mechanism remains unclear. In this study, a high-pressure supercooled molding experimental setup for melt-cast explosive is established. The effects of pressurization temperature and loading pressure on the solidification process of 2, 4-dinitroanisole (DNAN)-based melt-cast explosive are systematically investigated based on the principle of high-pressure subcooling non-equilibrium solidification. Then, the mechanism of the high-pressure subcooling accelerating the solidification and cooling processes of melt-cast explosive is revealed by using the conjugate gradient method and an actual contact area model. The results indicate that the melting and solidification points of the explosive increase and the critical subcooling degree decreases under high-pressure. The maximum actual subcooling degree occurs when the pressurization temperature coincides with the solidification exothermic peak temperature observed under atmospheric pressure, thus initiating high-pressure subcooling. This effect promotes the rapid release of solidification latent heat, which leads to a noticeable increase in temperature and a shortening of solidification time. The higher the loading pressure, the higher the temperature rise of the explosive, and the solidification time first decreases and then increases as the loading pressure increases. The plastic deformation of surface asperities of the grain subjected to pressure after solidification enhances the actual contact area ratio, thereby improving the interfacial heat transfer coefficient and shortening the cooling time. The total molding time is minimized at a pressurization temperature of 73.0°C and a loading pressure of 50.0MPa, reaching only 56.0% of that required under atmospheric pressure. The grain molded under this condition achieves a relative density of 99.9%, and no defect in it is detected by CT scanning.