MICROSTRUCTURE CONTROL OF TITANIUM ALUMINIDE POWDER COMPACTS BY THERMOCHEMICAL PROCESSING

Powder metallurgy of ordered alloys is not only a method to obtain net-shape products but is also an effective approach to microstructural refinement for improvement of some properties such as tensile ductility and fatigue strength. In the present study, prealloyed plasma rotating electrode process (PREP) powder was used to produce compacts with an ultrafine grain structure by employing conventional and hydrogen thermochemical processing routes. These processes are capable of producing a wide range of alpha-2 (alpha-2) structures, including an ultrafine microstructure with a grain size on the order of a micron. This paper will discuss some of the mechanisms leading to microstructure refinement with an emphasis on the role of hydride formation.