Ion bombardments, transmission-electron-microscopy (TEM) and analytical-electron-microscopy (AEM) techniques were used to obtain information on the effect of irradiation on the phase stability of Zr3 Fe, which has an orthorhombic crystal structure. Irradiations were performed at 35–773 K using 0.5–1.5 MeV 40Ar ions and at 40 K using 15–120 keV 209Bi ions.
At low ion fluences (1011–1013 ions cm−2), most of the visible damaged regions (∼1.0–5.0 nm diameter) exhibited strong structure-factor contrast features and it is believed that they are probably amorphous. With increasing ion energy, multiple damaged regions were observed to form within individual collision cascades, and the fraction of the theoretical cascade volume occupied by these heavily-damaged regions decreased rapidly. Irradiations at higher ion fluences showed that an irradiation-induced phase change from the crystalline-to-amorphous state occurred at 35–573 K, but not above 623 K. The effect of varying the ion flux was also investigated. The results showed that the fluence required to amorphize a given fraction of the irradiated volume was quite dependent upon the amount of annealing that occurred within the collision cascade at the temperature of the bombardment. The crystalline-to-amorphous transformation appeared to be the result of direct amorphization within the collision cascades and a critical defect concentration being reached in the cascade overlap regions, thus producing additional amorphous regions.