Decomposition mechanism of AlMgB14 during the spark plasma sintering

In this work, AlMgB14-based materials were obtained from an (Al-Mg)-B powder mixture by spark plasma sintering. The microstructure, phase composition, and properties of the obtained materials were investigated. The sample, which was sintered at a temperature of 1400 degrees C, has the highest average hardness of 29.5 GPa with a maximum measured hardness value of 34.55 GPa. The density of the obtained sample is 2.621 g/cm(3) (theoretical density of pure AlMgB14 is 2.59 g/cm(3)). A mechanism for the decomposition of AlMgB14 at local overheating of the (Al-Mg)-B powder mixture during spark plasma sintering was proposed. In the first stage, AlMgB14 decomposes into AlB12 , an intermetallic compound Al12Mg17 and Mg. In the second stage, the decomposition products react with oxygen to form spinel MgAl2O4 and aluminum borate Al4B2O9. Finally, the use of isothermal holding for 5 min at a temperature of 1470 degrees C leads to an increase in the MgAl2O4 spinel content, further reaction of Al2O3 and boron oxide B2O3 and, as a consequence, the formation of borate Al18B4O33. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

In this work, AlMgB14-based materials were successfully obtained by spark plasma sintering from an (Al-Mg)-B powder mixture, and their microstructure and properties were investigated. Samples sintered at high temperatures exhibited high hardness, and a mechanism for the decomposition of AlMgB14 during local overheating was proposed.