An in-situ TEM investigation on microstructure evolution of Ni-25Â 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 °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 °C. At 500 and 700 °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 °C. Moreover, it is found that the grain growth is relatively slow when the temperature is lower than 300 °C, while all of normal grain growth, abnormal grain growth and annealing twinning occur at higher temperatures.