Formation and interface structure of TiC particles in dispersion-strengthened Cu alloys

Abstract

TiC-dispersion-strengthened Cu alloys were prepared by mechanical alloying and subsequent hot extrusion. The evolution of the microstructure with respect to the preparation process is analysed by transmission electron microscopy techniques. The TiC dispersoids are formed in situ by the reaction of Ti and graphite. Ti diffuses from the pre-alloyed CuTi matrix to C inclusions which are embedded in the matrix after high-energy milling. Heat treatment of the powder mixtures at 400°C leads to heterogeneous nucleation of TiC at the C/Cu interface. Thereby a well defined cube-on-cube orientation relationship is established between TiC and the Cu matrix. A study of the morphology of the TiC dispersoids shows that they are faceted on {111}_TiC {110}_TiC and {100}_TiC planes and possess ledges on the atomic scale. The TiC/Cu interfaces are atomically abrupt and free of interface phases. The {100}_TiC∥{100}_Cu and ⟨110⟩_TiC∥⟨110⟩_Cu topotaxy leads to a misfit of 17.6% between the adjacent lattices. This misfit is accommodated by a dislocation network along ⟨100⟩_Cu directions.