Abstract
An investigation of microstructural development and structure-property relationships in a transient liquid phase bonded Ti-48Al-2Cr-2Nb at.- alloy abbreviated here to 48-2-2 is presented. The use of copper containing interlayers is examined. The primary focus of the paper is wide gap composite interlayers consisting of copper as a liquid former, plus a TiAl alloy binary TiAl or 48-2-2 as a non-melting diffusional sink. However, bonds employing commercial purity copper foils of thickness 5 and 50 m are also examined. Bond microstructures are characterised by edge-on transmission electron microscopy, plus scanning electron microscopy and light microscopy. Mechanical properties are determined through the use of room temperature shear and bend testing, supplemented by both room and elevated temperature tensile testing. The formation of copper containing intermetallics at the bond line and the formation of gamma-TiAl by both epitaxial growth and non-epitaxial precipitation are discussed. The microstructure of the bonds is compared with that of the parent 48-2-2 material. The influence of both the main bond line microstructure and the fillets on the mechanical properties of transient liquid phase bonded 48-2-2 is determined.
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