Effect of Prior Oxidation on Tensile Properties of Bare and Al_3Ti Diffusion Aluminide Coated Near a Titanium Alloy Titan 29A

摘要

The effect of prior oxidation, for various durations up to 2,000 h in air at 650 °C, on the room temperature tensile properties of uneoated and Al3Ti diffusion aluminide coated near a Ti alloy, Titan 29A, has been evaluated. The tensile properties of the uneoated alloy deteriorated with oxidation. Oxidation for just 100 h caused 11-13% decrease in yield strength (YS) and ultimate tensile strength (UTS) of the alloy. The uneoated alloy exhibited brittle fracture within the elastic regime at significantly lower stress after oxidation for 2,000 h. On the other hand, the strength of the coated alloy remained unaffected even after 2,000 h of oxidation and the YS and UTS was similar to that of the un-oxidized alloy. The ductility of the coated alloy, however, decreased with the increase in oxidation duration. Such differences in the tensile behavior of the uneoated and coated alloy can be ascribed to the beneficial effect of the Al3Ti diffusion aluminide coating in preventing surface embrit-tlement in the alloy during oxidation.