Microstructure and properties of a creep-resistant, cast γ-titanium aluminide

The microstructure and mechanical properties of an investment cast γ-aluminide containing small amounts of W, Mo and Si are described and a comparison is made with typical two-phase, first-generation aluminides exemplified by Ti-47Al-2Nb-2Cr, Ti-47Al-2Nb-2Mn and Ti-47Al-2Nb-2Mn-0.8vol.%TiB2 (all in at.% unless indicated otherwise). Tensile tests show that the WMoSi aluminide has good ductility and is intermediate in strength between the first-generation aluminides and a Ti-46Al-5Nb-1W aluminide. X-Ray diffraction analysis of the WMoSi aluminide indicates the presence of the B2 phase which is enriched in W, Mo, Mn and Nb. The B2 precipitates are present at the lamellar colony boundaries as well as at the lamellar α2γ interfaces.