Effect of reactive sintering conditions on microstructure of<i>in situ</i>titanium aluminide and silicide composites

Abstract

In this work, the dependence of microstructure of in situ titanium aluminide and silicide composites on chemical composition and conditions of reactive sintering was studied. It was found that the rate of reactive sintering process increases with growing silicon content. In addition, heating rate strongly affects the structure of Ti–Al–Si alloys with lower content of silicon represented by TiAl23Si10 alloy. The structure consisting of homogeneously distributed Ti5Si3 particles in TiAl matrix can be obtained by rapid heating over 250 K min−1 in this material. TiAl15Si15 alloy forms the desired two phase TiAl–Ti5Si3 structure when a heating rate of at least 10 K min−1 and temperature over 750°C are applied. Replacement of aluminium and silicon powders by Al–Si alloy positively affects the reactive sintering process. The structure of these materials can be refined by milling of Al–Si master alloy powder to the <100 μm fraction, reducing the size of Ti5Si3 particles and porosity significantly.