Al-Li계 합금에 있어서 δ상의 조대화 현상에 미치는 Cu와 Mg의 영향

Abstract

The coarsening behavior of δ′(AI₃Li) phase has been studied in various alloys of Al-Li, Al-Li-Cu and Al-Li-Cu-Mg systems using transmission electron microscopy. The coarsening kinetics are well governed by Ostwald ripening theory in all cases. The ccarsening rate depends sensitively on the volume fraction of δ′ phase particulary in binary system, which conforms relatively well to the MLSW theory. The addition of Cu in Al-Li binary alloy ○ds to accelerate the coarsening rate of δ′ phase. This is believed to be due to the variation of δ′ interfacial energy. The addition of Mg in Al-Li-Cu ternary alloy tends to reduce the δ′ coarsening rate. This is because the precipitation of S′ phase has an effect to reduce the diffusivity of Li atom by depleting the concentration of vacancy.