Precipitation behavior in the early stage of aging in an Al-Li-Cu-Mg-Zr-Ag (Weldalite 049) alloy

摘要

The precipitation behavior of various phases during the aging process of an Ag-Li-Cu-Mg-Zr-Ag (Weldalite 049) alloy was investigated by high-resolution electron microscopy and in situ hot-stage microscopy. Two kinds of domains with L12-type ordered structures, which are considered to be δ~l and β~1' phases, are observed with different domain sizes in the alloy quenched from 530 deg C. In the early stage of aging at l90 deg C, the δ~l phase is precipitated as surrounding the β~1 phase, and the 6l domains appear with in-phase and antiphase relationships to the β~1 lattices. In situ observations at l90 deg C clearly show that the T1 phase precipitates predominantly on dislocations at subgrain boundaries and then is homogeneously formed in the matrix with increasing aging time. The nucleation of the S~l phase is associated with clustering of Cu and Mg in the matrix, and the S' domains are grown with {2l0} habit planes.