Densification of a porous body during hot extrusion

Abstract

1. A theoretical analysis is made of the densification of porous, viscous Newtonian and non-Newtonian bodies during hot extrusion. Equations are derived expressing the variation of the pressure and discharge energy as functions of relative density, fluidity of the solid phase forming the porous body, the coefficient of elongation, and ram velocity. The equations are applicable also in the limiting case of hot extrusion of a nonporous body. 2. It is demonstrated that, with a porous body whose solid phase is incompressible, the nonporous state cannot be attained by hot extrusion, and the relative density of specimens grows with increase in the value of coefficient of elongation. 3. Published experimental data indicate that the equations derived correctly describe the process of hot extrusion of porous materials. Using data obtained for porous iron, it is shown that the hot extrusion ofγ-iron is accompanied by plastic flow with an energy of activation close to that for flow in dynamic hot pressing; the two processes also have the same index of nonlinearity of flow, n=4. 4. Equations are derived for the energy of extrusion of a porous body processed under dynamic conditions with shock loading.