CHARACTERIZATION OF EVOLUTION OF MICROSTRUCTURE DURING PROCESSING OF AL-LI-MG-CU-ZR CAST ALLOYS

The as cast microstructures of Al-2.5Li-2Mg-0.14Zr alloys containing 0, 0.1, 0.3, or 0.5% Cu are characterised and the phases present are identified. A combination of light microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction techniques was used. The changes accompanying subsequent treatments, i.e. homogenisation, hot deformation, solution treatment, and aging, have also been investigated. The Al6CuLi3 (T2) phase is found to be present in the form of tiny particles in a non-equilibrium eutectic in the as cast Cu containing alloys. This is responsible for the partial melting of these alloys at approximately 545-degrees-C. (C) 1993 The Institute of Materials.