Aluminium magnesium boride: Synthesis,sintering and microstructure

Abstract

AlMgB₁₄ ceramics were reported as high-hardness materials over a decade ago. While different synthesis routes for processing of AlMgB₁₄ ceramics were reported in the past, however the synthesis routes are still not optimised and present a significant challenge to the manufacturers. In this work six different synthesis routes were explored for the synthesis of AlMgB₁₄ powder. The synthesised compositions were characterised by XRD, where weight fractions of each phase were calculated by Rietveld refinement. The bulk ceramics were sintered using powder with the highest yield (93.2%) of AlMgB₁₄ phase by spark plasma sintering at 1315°C and 50 MPa. Both phase composition and microstructure of the sintered AlMgB₁₄ were characterised by XRD and SEM/EDS, which revealed the existence of AlMgB₁₄, MgAl₂O₄ and a small amount of unreacted Al. Hardness and indentation fracture resistance of AlMgB₁₄ ceramics were measured to be 26.7 ± 2.2 GPa and 5.59 ± 0.42 MPa m^1/2, respectively by Vickers indentation technique.