Abstract
Magnesium alloys with rare earth (RE) elements are promising structural materials exhibiting favourable mechanical properties at elevated temperatures. However, the processes occurring during early stages of precipitation in these alloys are still not completely understood. In this work positron lifetime spectroscopy combined with coincidence Doppler broadening was employed for investigation of early stages of precipitation in Mg-RE alloys. Presence of quenched-in vacancy clusters was observed after solution treatment of studied alloys. These quenched-in vacancy clusters are bound to RE solutes and thereby stabilized at room temperature. During natural aging, RE clusters are formed by vacancy-assisted long-range diffusion. In addition, hardness of studied materials increases and quenched-in vacancy clusters are annealed out during the course of natural aging. Simple model was developed to describe hardening during natural aging.
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