TEM Microstuctural Characterization of a 2091 (Al-Li-Mg-Zr) Alloy Subjected to Welding Operations

Abstract

For over two decades considerable effort has been directed towards the development of Al-Li base alloys with the objective of replacing conventional high aluminum alloys, due to the fact that lithium additions cause substantial reduction in density accompanied by significant increase in the elastic modulus, implying, therefore, in appreciable improvement in the specific properties of the resulting alloys. These properties depend on the miscrostucture evolution during heat treatment or welding cycle. The microstructure of the commercial Al-Li systems is complex due to the addition of alloying elements, which increases the number of the allowed stable and metastable phases. During the thermo-mechanical processing of the 2091 alloy, the probable metastable are δ’, GPB zones and S’, the stable phases are S, T2 and the high temperature R (1-3). Further, the Zr precipitates the Al3Zr. The present study deals with the microstructure evolution of welded joints of the 2091 alloy studied by transmission electron microscopy, TEM.