Mn₂AlB₂ MAB Phase: Synthesis via mechanical activation-assisted annealing, parameter optimization and characterization

The present study aimed to synthesize the Mn₂AlB₂ MAB phase from Mn/Al/B elemental powders using mechanical activation-assisted annealing. The effects of mechanical activation (for 1, 3, and 5 h), annealing temperature (900, 1100, and 1300 °C), and different starting Al ratios on the final products were examined. It was found that the ternary-boride phase formed as a single phase without ternary borides or intermetallic compounds when annealing samples with a Mn/Al/B ratio of 2/1.5/2 at 900 °C for 3 h after mechanical activation. Conversely, samples with a 2/1/2 starting stoichiometry contained some MnB in their structure, while those with a 2/2/2 ratio exhibited a high amount of Mn-Al intermetallics along with this phase. Additionally, increasing the annealing temperature led to a higher presence of impurity phases within the structure. Thermodynamic investigations and thermal analyses indicated that the synthesis of the Mn₂AlB₂ phase occurs through reactions between binary boride and intermetallic phases formed during annealing at higher temperatures, rather than by the direct reaction of elemental powders.