An in situ experimental study of grain growth in a nanocrystalline Fe91Ni8Zr1 alloy

Grain growth and microstructural evolution of thermally stabilized Fe91Ni8Zr1 were investigated by in situ and ex situ studies. Our investigations suggest that the microstructural evolution is fairly slow and the microstructure shows stabilization up to about 700 A degrees C. Above this temperature, a certain fraction of grains grow abnormally into the nanocrystalline matrix, resulting in a bimodal microstructure and causing the complete loss of thermal stability. The reason for abnormal grain growth and the loss of thermal stability is identified as the appearance of the fcc gamma-phase and consequent reduction in the total area of grain boundaries and the overall stored energy.