Method for heat treating gamma titanium aluminide alloys

A method producing a gamma titanium aluminide alloy article, comprising the steps of:

• providing a piece of cast gamma titanium aluminide alloy having a composition capable of forming alpha, alpha-2, and gamma phases, and a eutectoid in which alpha phase decomposes to colonies comprising alpha-2 and gamma phase upon cooling, the piece of cast gamma titanium aluminide alloy having an aluminum content of from about 45.5 to about 48.5 atomic percent
• consolidating the gamma titanium aluminum alloy piece at a temperature above the eutectoid to reduce porosity therein;
• first heat treating the gamma titanium aluminide piece at a temperature above the eutectoid for a time sufficient to form a structure of gamma grains plus lamellar colonies comprised of alpha-2 and gamma phases, wherein the step of first heat treating includes the steps of heating the piece to a temperature of from about 2100.degree. F. to about 2200.degree. F. for a time of at least 8 hours;
• and thereafter
• second heat treating the gamma titanium aluminide piece at a temperature below the eutectoid to grow gamma grains within the colony structure, thereby reducing the effective grain size of the colony structure, wherein the step of second heat treating includes the step of heating the piece to a temperature of from about 1800.degree. F. to about 2000.degree. F. for a time of at least about 8 hours.