Dimensional Stability and Microstructure Evolution in Irradiated Systems with Complex Kinetics
We use a combination of molecular dynamics and kinetic Monte Carlo simulations to explore the role of temperature and dose rate on damage accumulation in a model system with complex kinetics. We describe the accumulation of He-vacancy (HeV) complexes as well as vacancy and interstitial clusters as a function of irradiation temperature, dose, and dose rate. We show that nucleation of stable HeV complexes (voids and bubbles) at low temperature and flux takes place at extremely low doses. We also
... low doses. We also describe the effect of temperature on the HeV complex size distribution and show that growth beyond a critical nucleation size is not possible in this system at temperatures above 300 K for dose rates smaller than lo-' dpa/s. We further demonstrate that a temperature shift of 25 K per decade of flux scales the dose rate dependence of He-vacancy complex (voids and bubbles) accumulation when irradiation is carried out to low doses (0.03 -0.06 dpa) at temperatures between 150 K and 300 K and dose rates of 10'6, 10'7, lo-', and 10m9 dpa/s. The results provide an atomistic description of microstructure evolution including void nucleation and the early stages of growth, and should be useful in designing and interpreting accelerated aging experiments.