APPLICATION OF A THERMAL SPIKE MODEL TO EXPERIMENTAL ION-INDUCED GRAIN-GROWTH DATA

A model of ion-induced grain growth is developed incorporating the irradiation effect concept of thermal spikes. The results of the model predict that for normal grain growth the ion-induced mobility is linearly proportional to the quantity F(D)2/DELTA-H(coh)3, where F(D) is the ion and recoil energy deposited in nuclear interactions and DELTA-H(coh) is the cohesive energy. This linearity is shown to be supported by the data from six of seven previous ion-induced grain growth experiments. The model analysis is combined with the experimental data to determine values of the proportionality constant, beta(IIGG), relating the cohesive energy to the activation energy for grain growth (Q = -beta(IIGG)DELTA-H(coh)). The values are found to span a range, 0.05 less-than-or-equal-to beta(IIGG) less-than-or-equal-to 0.10, which is less than the value previously determined for the thermal spike treatment of ion beam mixing (beta(IM) = 0.14), and therefore consistent with the idea that atom migration across grain boundaries is easier than migration within the lattice. The consistency of results from the analysis of an entirely different phenomenon adds further credence to the thermal spike treatment of ion-induced grain growth. Finally, it is recommended that additional experiments be performed to evaluate further the model's validity.