The effect of Y2O3 on the grain growth and densification of W matrix during low temperature sintering: Experiments and modelling

Highlights: • Grain boundary diffusion is the mass transport mechanism in pure W and W-Y₂O₃ systems during the low temperature sintering. • During the intermediate stage of low temperature sintering, W skeleton densification is suppressed by Y₂O₃ addition. • The lower surface diffusion, smaller dihedral angle and wetting of W grain boundary cause the densification inhibition. -- Abstract: In this work, the effect of Y₂O₃ addition on the grain growth and densification of W matrix was explored from a kinetic perspective by comparing the low temperature sintering behavior of W-Y₂O₃ composite nanopowder system with that of pure W nanopowder system. By combining nonisothermal sintering experiment with the power law of grain growth, it was found that grain boundary diffusion is responsible for the mass transport mechanism in both systems. The inhibition of W grain growth after Y₂O₃ addition is closely related to the lower surface diffusivity of W skeleton. The densification rate of W skeleton in these two systems were modelled using a periodic 3D arrangement of identical particles and a much smaller grain boundary diffusivity of W skeleton was obtained for W-Y₂O₃ sample. Firstly, it is the decrease in dihedral angle of W matrix after Y₂O₃ addition that causes a decrease in thermodynamic driving force for densification. Secondly, from the view of atomic mobility, the inhibited W grain growth caused by limited surface diffusivity is one of the reasons impeding densification. Besides, Y₂O₃ grains distributed at W grain boundary coarsen through wetting W grain boundary, which also has an inhibition effect on the W skeleton densification.