An Experimental Study on the Effect of Microstructure on Oxygen Ingress in Ti-6242S Alloy

Excessive oxygen ingress at high temperature has been known to adversely affect the mechanical properties of alpha / beta Ti alloys. Although studies in the past have investigated oxygen ingress in Ti alloys, the impact of microstructure on the diffusion of oxygen and the formation of alpha case is only beginning to emerge. This study focuses on the roles of alpha orientation and morphology. Samples of Ti-6242S alpha / beta alloy were solutionized in a vacuum furnace and held at temperature to produce large beta grains. Slow cooling was used to produce large colony microstructures. The samples were subsequently oxidized at 650 degree C for 100 hours. The material was sectioned and analyzed using optical microscopy, SEM and EBSD techniques to investigate the effect of morphological orientation of (+) colony microstructure on oxidation. Additionally, the oxidized samples were examined for nucleation of surface cracks under tensile loads to determine effects of microstructure on mechanical performance.