Characterizations of Lamellar Interfaces and Segregations in a PST-TiAl Intermetallic Alloy by an Analytical Scanning Transmission Electron Microscope

Polysynthetically-twinned titanium aluminide (PST-TiAl), a fully lamellar γ-TiAl+α2Ti3Al dual-phase alloy, is under evaluation for applications in rotary components in aircraft and automobile industries due to its high specific strength, and a high strength-retention capability at elevated-temperatures. However, the low ductility at roomto mid-high temperatures of the material hinders its application. Additions of certain tertiary elements to the binary TiAl system appear to improve the ductility at roomto mid-high temperatures, thus a balance among strength, ductility, and fracture toughness can be expected. In this article, segregation of tertiary elements to the lamellar interfaces is investigated. Single crystals of a TiAl with 0.6% atomic percentage tertiary additions are grown by an optical float-zone method. Segregation to the lamellar interfaces and the microstructure of the interfaces are investigated. Structures of the lamellar interfaces are characterized, and microchemistry and distribution habits of these elements along the γ+α2 lamellar boundaries as well as the γ-γ lamellar and domain boundaries are analyzed. Comments Copyright Materials Research Society. Reprinted from MRS Proceedings Volume 652. 2000 Fall Meeting Symposium Y Influences of Interface and Dislocation Behavior on Microstructure Evolution Publisher URL: http://www.mrs.org/members/proceedings/fall2000/y/Y10_4.pdf This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/13 Characterizations of Lamellar Interfaces and Segregations in a PST-TiAl Intermetallic Alloy by an Analytical Scanning Transmission Electron Microscope Wei (Wayne) Zhao and David E. Luzzi Department of Materials Sciences and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104-6272