A STUDY OF THE PROBABILITY OF VACANCY LOOP FORMATION IN NI-CU AND AG-PD ALLOYS

The molten-zone model for vacancy loop formation from a displacement cascade predicts that the probability of loop formation should scale with the melting temperature. To investigate this Possibility the areal defect density, the loop size, and the vacancy retention factor have been determined in a series of Cu-Ni and Ag-Pd alloys. The irradiations were performed at room temperature with 50 keV Kr+ ions and the resulting damage structure was examined by using transmission electron microscopy. In the Cu-Ni alloy series, the vacancy retention factor decreased with increasing solute content (melting temperature) but not in a simple manner. The behavior in the Cu-Ni system could be predicted when the effect of heat removal through the electronic system on the lifetime of the molten zone was taken into account. In the Ag-Pd alloy the change in the vacancy retention factor followed more closely the change in melting temperature, heat removal through the electronic system appeared to have little effect.