Porosity of Nickel Nanopowder Compacts Consolidated by Gas Extrusion

This paper presents a method to calculate the pore gas pressure from the minimum size of a closed pore. The pore pressure assessment is based on materials produced by consolidation of nickel nanopowders using hot gas extrusion. Scanning electron microscopy shows that the minimum pore size is 220 nm. The pore pressure equation is derived from the equation for the critical pore radius. The equation takes into account the external impact pressure (gas pressure during the extrusion process was 400 MPa), surface tension coefficient, and the yield strength of nickel (at the initial extrusion temperature of 910 degrees C), as well as the minimum pore radius. The proposed method for calculating the gas pressure inside a closed pore provides an assessment of the mechanical properties of materials produced by different methods of powder metallurgy.