Thermal stability of the nanolayered Fe2AlB2 in nitrogen and argon atmospheres

The thermal stability and decomposition mechanisms of Fe2AlB2 powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N2) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe2AlB2 and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as‐synthesized Fe2AlB2 powders are treated in dilute HCl to dissolve impurity phases, decomposition in N2 atmospheres occurs readily above 1200 K. The decomposition reaction involves β‐FeB precipitation and the liberated Al atoms reacting with the ambient N2 to form AlN. Under Ar environments, HCl‐treated Fe2AlB2 powders decompose and precipitate β‐FeB, by the out‐diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N2 atmospheres revealed that Fe2AlB2 was more thermally stable when synthesized from lab‐synthesized, instead of commercially available, FeB precursors and when the HCl treatment was avoided. The effects of the various factors on the decomposition temperature and decomposition mechanisms are discussed herein.