SHORT-DURATION AND STRESS-RUPTURE STRENGTH OF BETA-ALLOY OF Ti-Mo-Cr-Fe-Al SYSTEM AT HIGH TEMPERATURES,

A beta-alloy of Ti contg. Mo 7, Cr 5.5, Fe 3, and Al 3 percent when quenched from 800 degrees and aged at 550 or 525 degrees for 15 hrs. at 500 degrees for 20 hrs., and at 450 degrees for 50 hrs. exhibits high mech. properties at elevated temps. When exposed to the anticipated working temp. 350 degrees for 100, 500, and 1000 hrs. its mech. properties are influenced slightly, indicating high thermal stability. To accomplish the heat-resistance tests, specimens 4 mm. in diam. were subjected to bending with the application of centrifugal force that permitted a simultaneous detn. of creep resistance and stress-rupture strength. The samples were tested at 350 degrees in the air and the rate of creep was assessed from bending inflection. The microstructure of strained samples after 250 hrs. testing differs slightly from that of initial specimens and the only change observable is the appearance of subgrain boundaries in primary beta-grains. Specimens quenched from 800 degrees and aged according to the regime A or B were tested as to heat resistance at 20-700 degrees. From 250 to 450 degrees their mech. strength varies slightly. At 500 degrees it decreases but still maintains relatively high values, 92 and 105 kgsq-mm for alloys aged at 525 and 550 degrees resp. Author