Accession Number : AD1043325


Title :   Fatigue Crack Growth and Fracture Behavior of As-Cast Ti-43.5Al-4Nb-1Mo-0.1B (TNM) Compared to Ti-48Al-2Nb-2Cr (4822) (Postprint)


Descriptive Note : Journal Article - Open Access


Corporate Author : Case Western Reserve University Cleveland United States


Personal Author(s) : Dahara,Matthew S ; Lewandowskia,John J ; Tamirisakandala,Sesh A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/1043325.pdf


Report Date : 17 Sep 2017


Pagination or Media Count : 13


Abstract : The effects of sample orientation and load ratio on the room-temperature fatigue crack growth and fracture behavior of a third-generation gamma titanium aluminide Ti-43.5Al-4Nb-1Mo-0.1B (TNM) were determined and compared with that of a second-generation alloy Ti-48Al-2Nb-2Cr (4822). Both materials are currently used as low pressure turbine blades in fuel-efficient gas turbine engines. Bend bar specimens, excised from the as-cast articles in the longitudinal and transverse directions to the casting direction, were tested at room temperature in lab air. Load ratios in the range 0.10.9 were used in fatigue testing to determine their effects on the fatigue threshold, Paris law slope, and stress intensity at overload in fatigue. Microscopy and fractography were used to document the effects of sample orientation on the fatigue crack path and morphology. Significant effects of changes in load ratio were observed on the fatigue threshold and Paris law slope, while effects of sample orientation were minimal for both alloys. The effects of microstructure length scale and differences in microconstituents are discussed in relation to the properties measured.


Descriptors :   titanium aluminide , turbine blades , fractography , crack tips , alloys , gas turbines , fatigue mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE