Dynamic compaction of titanium powder by vaporizing foil actuator assisted shearing

Abstract

Electrically driven rapid vaporization of thin metallic foils is known to create very high pressures, which can be harnessed for mechanical work. Recently, vaporizing foil actuators (VFA) have been applied to a variety of impulse-based metal working operations such as collision welding, embossing, shearing, shape calibration, and closed-die forming. Here, a variation of VFA has been used for dynamic compaction of metallic powders. Holes with a diameter of 10mm were sheared into Cu110 sheets using foil actuators operating at input electrical energies from 4kJ to 10kJ. During the impulse shearing operation, the sheared plugs were found to accelerate up to velocities of 1.4km/s within a few millimeters of travel distance. These sheared plugs were used as pistons to compress milled commercially pure titanium (CP-Ti) and Ti–6Al–4V alloy (Ti–6–4) powders, both of which had tap densities of approximately 25–28%. Cylindrical green compacts weighing ~2g were produced by this process. The densities of the compacts, measured using the Archimedes principle, were found to increase with input electrical energy. A maximum density of 97% was obtained with CP-Ti powder, while Ti–6–4 powder could be compacted to 93% dense. When compared to a quasistatic cold compaction process, a significant gain in densification with same pressures was observed.