The Effect of Lath Orientations on Oxygen Ingress in Titanium Alloys
- PDF / 718,847 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 141 Views
ODUCTION
TITANIUM is an excellent material choice for many structural applications where high specific strength and fatigue properties are required.[1,2] With the greater need for the improved specific fuel consumption and higher flight velocities, there is a great demand for structural materials to operate at higher temperatures.[3,4] Many studies have investigated the high-temperature properties of titanium alloys and their dependence on microstructural features. Researchers have shown that a colony size, a lath thicknesses, and crystallographic texture greatly impact plastic flow at hot forming temperatures and crack growth rates that drive fatigue.[5,6] Viswanathan et al.[7,8] used nanoindentation techniques to investigate the impact of orientation on hardness in Ti-6Al-2Sn-4Zr-2Mo+Si (Ti-6242S) with equiaxed alpha particles (approximately 20-lm diameter). Their research was aimed at identifying the dislocation structures associated with indent deformation, making it difficult to directly compare nanoindentation results for equiaxed a with microhardness data for other microstructures. Their research showed a 31 pct increase in the hardness measured for a (0001) orientations normal to the surface compared with (1120) and (10 10) orientations normal to the surface.[7,8] Additional research on the impact of texture on mechanical properties found that crystallographic oriJAIMIE TILEY, Senior Research Engineer, and ADAM PILCHAK, Research Engineer, are with the Air Force Research Laboratory, 2230 Tenth St., Wright Patterson Air Force Base, OH 45433. Contact e-mail: [email protected] JOSHUA SHAFFER, Research Engineer, and AYMAN SALEM, President, are with the Materials Resources LLC, 714 East Monument Ave, Suite 130, Dayton, OH 45402. ADAM SHIVELEY, Research Engineer, is with the UES, Inc., 4401 Dayton Xenia Rd, Beavercreek, OH 45432, and also with the Air Force Research Laboratory. Manuscript submitted November 6, 2012. Article published online October 10, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
entation affected both tensile ductility and high cycle fatigue strength.[9] In addition, oxygen diffusion during high-temperature application resulted in the formation of a brittle a-case layer and/or enriched oxygen regions at the surface of the material that significantly altered the mechanical properties.[10–13] Although the enrichment of oxygen results in dramatic reductions in ductility, it also may increase the wear resistance of the material, and the microstructural hardness.[10,14–16] Researchers often use the relationship between hardness and oxygen content to estimate the diffusion of oxygen into titanium alloys.[17,18] For example, Chan et al.[10] used the oxygen content to estimate the microhardness profile and extent of a-case formation in titanium alloy castings. They applied a power law model to estimate a-case thickness as a function of cooling rate for Ti-6Al4V, and then used a variety of models to predict tensile ductility and wear resistance.[10] This approach relied on the estimation of oxygen diffus
Data Loading...
