Precipitation of metastable δ′ in Al–1·9Li–2·5Mg alloy

Metastable δ′ precipitates formed at 473 K in Al–1·9Li–2·5Mg alloy have been studied via specific heat measurements, analytical transmission electron microscopy, and atom probe field ion microscopy. The peak temperature of heat absorption associated with the resolution of δ′ into the matrix increases by more than 45 K after prolonged aging, i.e. the thermal stability of δ′ is enhanced by the aging treatment. The coarsening of δ′ obeys Ostwald ripening kinetics. However, the increase in the peak temperature is not related to the increase in size of δ′ but is instead attributed to an increase of the Mg content in δ′ precipitates; presumably, δ′ changes from Al3Li to (Al, Mg)3Li.MST/1846