Collapse of interconnected open Pores in Solid-State Sintering of W-Ni

Abstract

The closing behavior of interconnected open pores has been investigated in W-Ni systems where the dominant sintering mechanism is grain boundary diffusion. The samples were prepared by conventional powder metallurgy technique with large W particles containing Ni contents of 0.03 to 0.1 wt pct. The microstructure analysis indicated that pore collapse predominantly occurs at the three grain junction midpoints and produces closed pores at the four grain corners. The observed critical porosity, below which all the pores exist in isolated form, was found to be about twice as great as the critical porosity predicted by morphological perturbation theory. From these results, it is concluded that the grain boundary diffusion flux across the pore surface, as well as the capillary force, plays an important role in the closing behavior of interconnected open pores.