Internal friction measurements have been performed in order to study the Li mobility in Al‐Li alloys. Coherent &dgr;′ precipitation (nonequilibrium diffusion process) promotes a low temperature background increase according to Schoeck’s theory. A stablePzrelaxation has been observed at around 460 K (∼1 Hz). The analysis of the behaviour of this relaxation allows us to identify thePzpeak with the Zener relaxation associated to the stress induced Li‐Li pairs reorientation. The relaxation parameters lead us to determine the activation energy and the diffusion coefficient of Li. Zener relaxation has been observed in Al‐Li alloys. ©1995 American Institute of Physics.