Creep and densification during anisotropic sintering of glass powders

Abstract

The isothermal sintering behaviour of a barium magnesium aluminosilicate glass powder at 930°C was investigated using a heating microscope. The cylindrical samples exhibited a variable shrinkage anisotropy during sintering. The shrinkage anisotropy ratio, defined as the ratio of the relative change of height and diameter, varied linearly between ∼0.3 and ∼0.98 with the relative volume shrinkage during densification. Shrinkage anisotropy caused creep deformation of the samples. The creep rate varied exponentially with the densification rate and the ratio of creep to densification rates, ${{\dot \varepsilon _{\text{c}} } \mathord{\left/ {\vphantom {{\dot \varepsilon _{\text{c}} } {\dot \varepsilon _\rho }}} \right. \kern-\nulldelimiterspace} {\dot \varepsilon _\rho }}$, decreased as densification proceeded. This is in disagreement with most previous studies, which show a constant value of ${{\dot \varepsilon _{\text{c}} } \mathord{\left/ {\vphantom {{\dot \varepsilon _{\text{c}} } {\dot \varepsilon _\rho }}} \right. \kern-\nulldelimiterspace} {\dot \varepsilon _\rho }}$ during the densification. Overall, the study points out the relevance of variable shrinkage anisotropy and how it affects the densification behaviour of glass powders.