Microstructural Design for Improved Mechanical Behaviour of Advanced Materials
J. Phys. IV France 10 (2000) Pr6-15-Pr6-20
Variations in the α2/γ lamellar microstructure in Ti48Al alloys as a function of cooling rate and oxygen contentF. Perdrix, M. Cornet, J. Bigot and J.-P. Chevalier
CECM- CNRS, 15 rue Georges Urbain, 94407 Vitry-sur-Seine cedex, France
The α2γ lamellar microstructure in Ti-Al alloys is currently considered as promising and a study of microstructure as a function of cooling rate is presented. Appropriate microstructural parameters, such as α2 volume fraction, average width of the α2 plates, average spacing between them and grain size, have been measured by scanning electron microscopy and image analysis procedures. These measurements have then been systematically correlated with the cooling rate and the oxygen content of both commercial purity, oxygen doped and ultra high purity synthetic alloys. This has enabled clear trends between different cooling rates, microstructural parameters, hardness and yield stress to be established. The α2 volume fraction is seen to be a dominant feature. The yield stress follows a Hall-Petch type relation with the interlamellar spacing as the determining length scale. Finally, the stability of the lamellar microstructure will be briefly discussed.
© EDP Sciences 2000