CAST STRUCTURE AND PROPERTY VARIABILITY IN GAMMA-TITANIUM ALUMINIDES

Aspects of cast structure that influence mechanical property variabili ty, and in particular tensile ductility, have been studied in a Ti-48A l-2Cr-2Nb titanium aluminide alloy. Macrostructure, porosity, microstr ucture and tensile properties have been characterized over a range of casting processing conditions. Local solidification times and subseque nt solid-state cooling rates during casting have been characterized vi a local thermal measurements in combination with solidification modeli ng. Large variations in cooling rate during casting dramatically influ ence the initial cast structure as well as the distribution of defects such as porosity. Variations in as-cast structure persist through sub sequent thermal and hot isostatic pressing cycles and contribute to th e variability of tensile ductility. The current understanding of the r elationship of tensile ductility to processing-induced changes in stru cture will be briefly discussed. (C) 1998 Published by Elsevier Scienc e Limited. All rights reserved.