An in-situ TEM investigation on microstructure evolution of Ni-25 at.% Al thin films

The microstructure evolution of Ni-25 at.% Al thin films prepared by magnetron co-sputtering is investigated by using in-situ transmission electron microscopy (TEM) study from room temperature to 750 deg. C. The diffraction rings of both Ni and Al are present in the selected area electron diffraction (SAED) of as-deposited films, and then the diffraction ring of Al disappears when the films are heated up to 300 deg. C. At 500 and 700 deg. C, the diffraction rings and spots of L12 intermetallic Ni3Al phase are found, respectively, which means that the formation of ordered Ni3Al phase starts from 500 deg. C. Moreover, it is found that the grain growth is relatively slow when the temperature is lower than 300 deg. C, while all of normal grain growth, abnormal grain growth and annealing twinning occur at higher temperatures.