Cyclic Deformation of a Modern TiAl Alloy at High Temperatures

Abstract:

Ternary TiAl alloy with 8 at.% Nb and lamellar microstructure is subjected to low cycle fatigue tests at temperatures ranging from room temperature to 800 °C. The aim of the study is to find limit conditions when the microstructure is still stable and to study mechanisms of microstructural degradation when this limit is exceeded. Up to 750 °C, no cyclic softening or hardening is observed and cyclic stress-strain curve follows the tensile curve. Cyclic softening is characteristic for 800 °C. The TEM observation did not reveal any substantial changes in the microstructure due to the cycling up to 700°C. The lamellar structure is altered by cyclic straining at 750 °C and, to a higher extent, at 800°C. In specimens cycled to fracture at 800 °C, the domains without lamellar structure cover about 10% of volume and are almost dislocation free. The destruction of lamellar microstructure is the reason for the marked cyclic softening at 800 °C.

• Periodical: Advanced Materials Research (Volumes 891-892)
• Pages: 1131-1136
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.891-892.1131
• Online since: March 2014
• Authors: Tomáš Kruml, Alice Chlupová, Karel Obrtlík
• Keywords: Dislocation, High Temperature Fatigue, Lamellar TiAl Alloy, Low Cycle Fatigue, Microstructure

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