Study on the Crystal Structure and Microstructure Evolution of Shock-processed Titanium Powder

Titanium powder was rapidly solidified by using shock-wave consolidation technique.The critical parameters were controlled by intrumented detonics and pin-oscillography.The compacted specimens were investigated for crystal structure and microstructural strengthening by using standard diagnostic techniques.The density of the final product was found to be greater than 96% of the theoretical value.X-ray diffraction pattern reveals intact crystalline structure without the presence of any undesired phases.The particle size reduction indicated by XRD was supported by laser diffraction based particle size analyzer.Results from energy dispersive spectroscopy ruled out the possibility of any segregation within the compacts.Scanning electron microscopy showed crack-free,voids-free,melt-free,fracture-less compacts of titanium with a unidirectional dendrite orientation without any grain-growth.

A Constitutive Modeling and Experimental Effect of Shock Wave on the Microstructural Sub-strengthening of Granular Copper

Micro-sized copper powder(99.95%;O≤0.3)has been shock-processed with explosives of high detonation velocities of the order of 7.5 km/s to observe the structural and microstructural sub-strengthening.Axisymmetric shock-consolidation technique has been used to obtain conglomerates of granular Cu.The technique involves the cylindrical compaction system wherein the explosive-charge is in direct proximity with the powder whereas the other uses indirect shock pressure with die-plunger geometry.Numeric simulations have been performed on with Eulerian code dynamics.The simulated results show a good agreement with the experimental observation of detonation parameters like detonation velocity,pressure,particle velocity and shock pressure in the reactive media.A pin contactor method has been utilized to calculate the detonation pressure experimentally.Wide angled x-ray diffraction studies reveal that the crystalline structure(FCC)of the shocked specimen matches with the un-shocked specimen.Field emissive scanning electron microscopic examination of the compacted specimens show a good sub-structural strengthening and complement the theoretical considerations.Laser diffraction based particle size analyzer also points towards the reduced particle size of the shock-processed specimen under high detonation velocities.Micro-hardness tests conducted under variable loads of 0.1 kg,0.05 kg and 0.025 kg force with diamond indenter optical micrographs indicate a high order of micro-hardness of the order of 159 Hv.Nitrogen pycnometry used for the density measurement of the compacts shows that a compacted density of the order of 99.3%theoretical mean density has been achieved.