Pore formation mechanism and intermetallic phase transformation in Ti–Al alloy during reactive sintering

Abstract

The mechanism of pore formation associated with intermetallic reaction is studied in sintered Ti50Al50 alloy with two different heating rates i.e. 1 °C/min and 10 °C/min. The heating rate significantly influences the pore parameters and the intermetallic reactions. The pore size and porosity increase with the extent of exothermic reactions during sintering. The intermetallic Ti2Al5 phase forms by a low-temperature solid-state diffusion of Al at the surface of Ti skeletons, while TiAl3 and TiAl2 intermetallic phases form at a high temperature owing to Ti2Al5 phase reaction with Al and Ti, respectively. A considerable change in thermal and volume expansion take place in the alloy heated with 10 °C/min compared to 1 °C/min. Therefore, it is found that the heating rate during sintering greatly influences the porous properties of Ti50Al50 by controlling the degree of exothermic reactions.

Keywords

• Titanium aluminide
• Heating rate
• Intermetallic compound
• Exothermic reaction