Effect of Nitrogen Addition on the Microstructure and Mechanical Properties of Cast γ Titanium Aluminide Alloys

Abstract

Ti-(30∼38 mass%)Al-(0∼1 mass%)N alloys prepared by a precision casting method were investigated.The addition of nitrogen was found to be effective in refining TiAl/Ti3Al lamellar grains. Two-phase nitride particles composed of TiN as a core and Ti2AlN as an outer shell, together with fine precipitates of Ti3AlN, were identified in the present alloys containing nitrogen. The room-temperature ductility and strength increased with increasing nitrigen content up to about 0.3 mass%N, while they were decreased by further addition of nitrogen. The improvement in the room-temperature mechanical properties is mainly caused by grain refining and precipitation hardening.