The Role of Thermal Energy in Shock Consolidation

Abstract

Dynamic consolidation has considerable potential for densifying high strength materials which are very difficult to sinter by conventional techniques. Formation of dense compacts requires the collapse of the gaps between the particles as well as considerable amount of energy deposited at the particle surfaces for interparticle bonding. The ultra rapid deformation and energy deposition in shock consolidation produces partial melting at the particle surfaces followed by a rapid solidification via heat conduction into the interior of the particles. A series of attempts have been made by a number of investigators to consolidate these difficult-to-consolidate powders [1–6]. However, there exist two major problems. One is cracking of the compacts at both the microscopic and macroscopic level. The other is a lack of uniformity in microstructure and mechanical properties within the resulting compacts. Three novel approaches have been implemented: (1) shock consolidation of pre-heated specimens; (2) shock densification at a low pressure (just above threshold for pore collapse) followed by hot isostatic pressing (hipping); (3) use of local shock-induced reactions to increase temperatures of particle interfaces and enhance bonding. Fig. 1 shows, in a schematic fashion, these three approaches.