[PO-I2] Poster Session 2

[P2-74] Grain-Growth in Nanocrystalline Metals under Ion Irradiation: A Thermal Spike Model

^○Djamel Kaoumi¹, Robert Birtcher², Arthur Motta³ (1.North Carolina State University, United States of America, 2.Argonne National Laboratory, United States of America, 3.Penn State University, United States of America)

Grain growth was observed in nanocrystalline metallic foils in situ in a transmission electron microscope in a wide range of irradiation doses, temperature (from 20K to 773K) for four different pure metals (Zr, Pt, Cu and Au). The average grain size increased monotonically with ion fluence and similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type:. With respect to temperature, the experimental results showed the existence of a low-temperature regime (below about 0.15-0.22Tm), where grain growth is independent of the irradiation temperature, and a thermally assisted regime where grain growth is enhanced with increasing irradiation temperature. A model is proposed to describe grain growth under irradiation in the temperature-independent regime, based on the direct impact of the thermal spikes on grain boundaries. In the model, grain-boundary migration occurs by atomic jumps, within the thermal spikes, biased by the local grain-boundary curvature driving. The experimental results will be presented as well as the model proposed to describe grain-growth kinetics in the low-temperature regime (cryogenic temperatures).