Effect of milling on properties and consolidation of AlN by high-frequency induction heated sintering

Commercial AlN powders were high-energy ball milled for various durations, and consolidated without a binder, using the high-frequency induction heated sintering method (HFIHS). The effect of milling on the sintering behavior, crystallite size and mechanical properties of AlN compacts were evaluated. A dense AlN compact with a relative density of up to 96% could be readily obtained within 1 min. The ball milling effectively refined the crystallite structure of AlN powders, and facilitated the subsequent densification. The sinter-onset temperature was reduced appreciably, by the prior milling for 10 h from 750°C to 600°C. Accordingly, the relative density of AlN compact increased, as the milling time increased. It is clearly demonstrated that a quick densification of AlN bulk materials to near the theoretical density could be obtained by the combination of HFIHS and the preparatory high-energy ball milling process.