Order-sintering of mechanically alloyed FeAl nanostructures

In this work, FeAl intermetallic compounds were prepared by mechanical alloying and subsequent sintering processes. The powder milled for 80 h was found to be disordered Fe(Al) nanocrystals with 15 nm in size, which was sintered at 900 and 1000 °C for 1, 3 and 5 h. X-ray diffraction studies of the samples revealed a microstructural evolution and ordering during sintering. At both the sintering temperatures, the long-range order parameter first increased due to the promotion of ordered FeAl from the disordered Fe(Al) solid solution and then decreased by increasing the sintering time. This behavior was attributed to an increase in the concentration and clustering of thermal vacancies. It was also found that by increasing the sintering time, the crystallite size and lattice strain decreased, whereas the relative density and hardness increased.