Process for producing forged amp;agr;-2 based titanium aluminides having fine grained and orthorhombic transformed microstructure and articles made therefrom

摘要

Process for improving the mechanical properties and ultrasonic inspection efficiency of alpha-2 titanium aluminide forged products, parts or components and for preserving or retaining these improved properties at use temperatures up to about 1200° F. The process involves heating a billet of the alloy below its beta transus temperature, forging the heated billet within a true strain range of about 1.2 and 1. 4 and within a strain rate of about 0.1 and 0.15 per second to produce 90% refinement of prior &bgr; grains to a typical size less than about 0.2 mm, preferably about 0.02 mm, and cooling the forged billet to room temperature. A heat-treatment may be applied by rapidly cooling to room temperature to form the transformed beta phase with no precipitation of alpha platelets, and then heating to a transformation temperature (T) for a period of time (t) to form a beneficial orthorhombic crystalline phase microstructure including very fine alpha-2 particles, and not heating the alloy again above the use temperature of 1200° F., whereby the beneficial microstructure is retained and remains stable for extended periods of exposure at or below 1200° F.