Thermal stability of the nanolayered Fe 2 AlB 2 in nitrogen and argon atmospheres

The thermal stability and decomposition mechanisms of Fe 2 AlB 2 powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N 2 ) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe 2 AlB 2 and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as‐synthesized Fe 2 AlB 2 powders are treated in dilute HCl to dissolve impurity phases, decomposition in N 2 atmospheres occurs readily above 1200 K. The decomposition reaction involves β‐FeB precipitation and the liberated Al atoms reacting with the ambient N 2 to form AlN. Under Ar environments, HCl‐treated Fe 2 AlB 2 powders decompose and precipitate β‐FeB, by the out‐diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N 2 atmospheres revealed that Fe 2 AlB 2 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.