Effect of reactive sintering conditions on microstructure of in situ 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.

Keywords:

• Microstructure
• Composite materials
• Ttitanium aluminide
• Titanium silicide
• Reactive sintering
• Self-propagating high temperature synthesis

Acknowledgement

The research of Ti–Al–Si intermetallics was financially supported by the KJB201250801 research project of the Grant Agency of the Academy of Sciences of the Czech and by the research project of Ministry of Education, Youth and Sports of the Czech, MSM 6046137302.