**Table 2.**

*Roughness of dendritic and interdendritic regions.*

**Table 2** shows the results of roughness measurements carried out to evaluate the changes induced by the irradiation dose increase on the lamellae morphology of Ni(Si) and Ni3Si-monoclinic phases.

Results analysis shows that the roughness increase rate in the dendritic region is a dose function, an expected result based on the mathematical models of sputtering yield [16]. However, the roughness rate change in the interdendritic region shows a pronounced increase at a dose of 80 dpa, behavior that denotes the effect of Ni(Si) phase preferential erosion, but at a dose of 380 dpa the roughness value decreases markedly. This could be caused by a smoothing mechanism generated by mass transport as a consequence of the irradiation temperature, in order to determine the nature of this surface smoothing mechanism, the geometric factors of the pattern of valleys and ridges generated in the interdendritic region were measured.

Measurements of interdendritic regions' height profiles show a significant change pattern geometry of valleys and ridges formed in that region due to the preferential sputtering generated by the chemical composition of the phases that form the regular eutectic. **Figure 12** shows the diagram of the valley-ridges pattern, as well as the comparative height profile of the dendritic and interdendritic regions at both irradiation doses. **Table 3** shows the average results of the valley- ridges pattern geometric characteristics at both irradiation doses.

When analyzing the results of **Table 3** in conjunction with **Figure 12**, it is concluded that with increasing irradiation dose an additional sputtering mechanism with a geometrical character is present and it is this mechanism that is responsible for irradiated smoothing surface at a dose of 380 dpa. The theoretical foundation of this geometric erosion mechanism was provided by the erosion mechanism proposed by Sigmund [16].
