OXIDATION-KINETICS AND MICROSTRUCTURE OF V-(4-5) WT-PERCENT CR-(4-5) WT-PERCENT TI ALLOYS EXPOSED TO AIR AT 300-650-DEGREES-C

We conducted a systematic study to determine the effects of time and t emperature of air exposure on the oxidation behavior and microstructur e of V-4Cr-4Ti and V-5Cr-5Ti alloys. All samples were from 1 mm thick cold-rolled sheets, and each was annealed in vacuum at 1050 degrees C for 1 h prior to high-temperature exposure. Different samples from eac h alloy were heated in ambient air at 500 degrees C for times ranging from 24 to approximate to 2000 h, and in a thermogravimetric analysis (TGA) apparatus at temperatures ranging from 300 to 650 degrees C. Mod els describing the oxidation kinetics, oxide type and its thickness, a lloy grain size, and depth of oxygen diffusion in the substrate alloy were determined for the two alloys and compared. The results showed th at the oxide layers that formed on the surfaces of both alloys in air at 300-650 degrees C are protective, and that the V-5Cr-5Ti alloy is s lightly more oxidation-resistant than the V-4Cr-4Ti alloy.