INVESTIGATION OF REACTION MECHANISM IN SINTERING OF Al-TiB_2 COMPOSITES FROM ELEMENTAL POWDERS

摘要

In this work we investigated the reaction mechanism in the reactive sintering of Al-TiB_2 composites from elemental powders. Both thermal effects and phase formations in the sequence of the reactions leading to the in-situ TiB_2 formation were studied. Thermal effects were measured with high-temperature DSC, and XRD analysis was done on -intermediate- reaction products. Combination of results from these techniques show that after melting of Al, the first reaction is between Al and B, forming AlB_2. This is followed by a reaction between Al and Ti, forming Al_3Ti. The AlB_2 phase is melting incongruently at a temperature close to 1000 °C. This incongruent melting is followed by a reaction between Ti and B in solution leading to in-situ TiB_2 formation. The results show that the Al-B interaction is very important in the reactive sintering process.