Role of Ti۳AlC۲ MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part III: microstructure

In this paper, the ۳rd part of a series of publications on the sinterability and characteristics of TiAl–Ti۳AlC۲ composites, the microstructure development during the synthesis and sintering processes was studied by scanning electron microscopy (SEM). Chemical evaluation of various phases in the developed microstructures was performed using energy-dispersive X-ray spectroscopy (EDS) in different ways such as point, line scan and two-dimensional elemental map analyses. For this purpose, five samples were fabricated with different percentages of Ti۳AlC۲ MAX phase additive (۱۰, ۱۵, ۲۰, ۲۵ and ۳۰ wt%). Ball-milling and spark plasma sintering (SPS: ۹۰۰ °C/۷ min/۴۰ MPa) of as-purchased Al and Ti powders with already-synthesized Ti۳AlC۲ additive were selected as composite making methodology. SEM/EDS analyses verified the in-situ manufacturing of TiAl/Ti۳Al intermetallics as the matrix during the SPS process and the presence of Ti۳AlC۲ as the ex-situ added secondary phase. Moreover, the in-situ synthesis of Ti۲AlC, another member of MAX phases in Ti-Al-C system, was also detected in titanium aluminide grain boundaries and attributed to a chemical reaction between TiC (an impurity in the initial Ti۳AlC۲ additive) and TiAl components.

Keywords:

Microstructure , SPS , In-situ synthesis , TiAl–Ti۳AlC۲ composites , SEM/EDS analysis