Microstructural Evolution of Al-Li and Al-Li-Cu-Mg Alloys

摘要

Since subsequent microstructures and properties depend upon initial decomposition processes, the early developments in a binary Al-Li and quaternary Al-Li-Cu-Mg alloy were observed by high resolution transmission electron microscopy. Interpretation of high resolution images involved appropriate image simulations. The as-quenched microstructure was found to consist of small ordered domains which were unaffected by the presence of Cu and Mg alloying additions, BETA' (Al3 Zr) dispersoids and grain boundaries, and are thus interpreted as forming by spinodal decomposition. The ordered domains, approximately 4 nm in diameter, were often observed in antiphase with each other and were separated by regions of disordered matrix. No discrete delta' (Al sub 3 Li) particles were observed for natural aging times between 24 hours and 3 weeks.