Effect of annealing on microstructure and mechanical properties of large dimensional bulk nanocrystalline Fe–Al–Cr alloy prepared by aluminothermic reaction

Microstructure and mechanical properties of large dimension bulk nanocrystalline Fe–Al–Cr alloy after being annealed at 1073 K for 16 h and at 1273 K for 8 h, 16 h, and 24 h were investigated. It was shown that microstructure of the alloy after the annealing consisted of a nanocrystalline phase with a small amount of micron-sized Cr7C3 phase. The crystal structure of the alloy did not change and still kept the disorder bcc structure after annealing. With the increase of annealing temperature and time, average grain size of the nanocrystalline phase increased, and shape of the Cr7C3 phase transformed from needles to particles. The alloy after annealing had more stable deformation capacity and high strength in the compression at room temperature, and yield strength of the alloy after annealing was about triple the time of the Fe3Al based alloy with microcrystalline structure. The strength of alloy decreased after annealing at 1273 K for 24 h.