X-RAY-DIFFRACTION STUDY OF RESIDUAL-STRESS MODIFICATION IN CU W SUPERLATTICES IRRADIATED BY LIGHT AND HEAVY-IONS/

The effect of low temperature ion irradiation on the residual stress s tate was studied as a function of the ion fluence in Cu/W superlattice s prepared by ion beam sputtering. The residual stress tensor in tungs ten layers is completely determined from X-ray diffraction data using the ''sin2psi method''. In the as-prepared state, the Cu/W superlattic es are strongly strained, and we find in-plane compressive stresses as high as 6.4 GPa in tungsten layers. Relaxation of the stress state is observed after low temperature ion irradiation with increasing dose. This phenomenon is almost complete for doses as low as 0.1-0.2 dpa, an d appears related to atomic rearrangement in the elemental layers rath er than interfacial mixing. The role of the incident particle mass is also evidenced. Per dpa, heavy ion irradiation (Kr) induces the strain relaxation more quickly than light ions (He).