Material Phase Transformations Due To Shock Wave Loading In Contact Geometry
Free (open access)
197 - 206
A. K. Sharma
When an explosive is detonated, it generates a transient shock wave in the medium. The shock wave energy turns out to be invigorating with insuperable power when used in a more convenable, advantageous and efficacious manner. This shock wave, when it propagates through the material, produces new phases/transformations. The monolithic materials thus formed have important technological applications. This paper describes the experimental technique used to synthesize the newer materials under shock wave loading and the characterization of post shock compacts by means of spectroscopic and other methods. Hexagonal boron nitride powder has been transformed into its cubic structure by loading the material by shock waves. X-ray analysis of the recovered samples with I/I0 = 8 at d = 1.808 (angle 2Ǿ = 50.40) has indicated complete conversion of h-BN to c-BN. Super alloy powders of IN 718 and EP 741 NP of various chemical compositions and unique physical properties have been shock compressed. In EP 741 NP, the dendritic structure has been clearly observed in the centre with dendrites oriented in the radial direction, which happens to be the direction of heat flow. The structure needed for best results has been obtained. In IN 718, the dendritic structure within the particle is intact. The structure in the outer portion is better with satisfactory microstructure since the grain boundary has undergone solidification. Explosive compaction of a mechanical mixture of 80Ni-15Fe-5Co of grain size of about 30 nanometres has also been carried out for magnetic applications to study the effect of particle morphology. SEM analysis has indicated that the crystalline structure is intact in the shock-compressed specimens. Keywords: dendritic structure, IN 718, EP 741 NP, 80Ni-15Fe-5Co, particle morphology, SEM analysis, X-ray analysis, diffractogram, mechanical mixture, microstructure.
dendritic structure, IN 718, EP 741 NP, 80Ni-15Fe-5Co, particle morphology, SEM analysis, X-ray analysis, diffractogram, mechanical mixture, microstructure