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 c ascade predicts that the probability of loop formation should scale wi th the melting temperature. To investigate this Possibility the areal defect density, the loop size, and the vacancy retention factor have b een 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 resul ting damage structure was examined by using transmission electron micr oscopy. In the Cu-Ni alloy series, the vacancy retention factor decrea sed with increasing solute content (melting temperature) but not in a simple manner. The behavior in the Cu-Ni system could be predicted whe n the effect of heat removal through the electronic system on the life time of the molten zone was taken into account. In the Ag-Pd alloy the change in the vacancy retention factor followed more closely the chan ge in melting temperature, heat removal through the electronic system appeared to have little effect.