Oxidation and hardness profile of V–Ti–Cr–Si–Al–Y alloys

Several alloys of composition V–4Ti–4Cr–(0–0.5)Si–(0–0.5)Al–(0–0.5)Y were selected for oxidation in air. In addition a V–4Ti–4Cr–0.5Si–0.5Al–0.5Y alloy was pre-implanted with helium to study the effect of helium on oxidation behavior. Rapid oxidation experiments in air were conducted on tensile specimens and disc bend specimens at 300°C, 500°C, 600°C and 700°C for 1 h. After oxidation, tensile specimens were mounted in cross-section, and micro-indentation hardness tests were conducted. The depths of increased hardness obtained by indentation tests and the thickness of cleavage fracture zones measured by using scanning electron microscopy (SEM) micrographs were similar. The hardness profile of the cross-section in the depth direction corresponded to a model of oxygen diffusion in vanadium. Three-point bend tests were conducted on helium-implanted and air- exposed disc specimens. The bending stress of the specimen with 700 appm helium was larger than that with 70 appm helium.