Spatial instability of a system of primary defects under cascade damage

We consider the microstructure evolution of a non-equilibrium system of primary defects, in which mobile point defects, vacancy loops, and sessile interstitial clusters are continuously produced by cascade damage irradiation. The stability of a spatially homogeneous microstructure is analysed. It is found that in fully annealed metals the homogeneity may become unstable when the yield of vacancy clusters in collision cascades is sufficiently low. The bifurcation parameter and the critical wavelength of the developing heterogeneity are determined as a function of the damage rate, temperature, and clustering fractions of vacancies and interstitials. It is also found that the case of only vacancy loop generation does not correspond to the limiting case of low interstitial cluster production when vacancy loops and interstitial clusters are produced simultaneously.Department of Mechanical Engineerin