Comparison of electron and ion irradiation effects on order—disorder transition in Ni 4Mo

Abstract

The effects of radiation damage in metals and alloys caused by electron and heavy ion beams are quite distinct from the consideration of cascade formation. Microstructural changes occurring with progressive dose of irradiation under cascade forming heavy ion irradiation and under electron irradiation have been systematically studied in Ni 4Mo in the temperature range of 300 to 1050 K. The ordering transformation in this alloy can be used in understanding the fundamental processes of radiation damage. Conversely, radiation experiments provide an insight into the ordering mechanisms. The ordering in this alloy is governed by a competition between a second order and a first order ordering process. Steady state structures developed at different temperatures have been characterised by electron diffraction and imaging. The steady state diagrams are constructed and compared for both electron and ion irradiation. The essential difference between the nature of cascade forming and non-cascade forming irradiation on the order—disorder transformation has been discussed.