Microstructure evolution and mechanical properties of an intermetallic Ti-43.5Al-4Nb-1Mo-0.1B alloy after ageing below the eutectoid temperature

Limei Cha, Helmut Clemens, Gerhard Dehm*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Intermetallic γ-TiAl based alloys with a chemical composition of Ti-(42-45)Al-(3-5)Nb-(0.1-2)Mo-(0.1-0.2)B (in atom percent) are termed TNM alloys. They exhibit several distinct characteristics, including excellent hot-workability and balanced mechanical properties. In this study, the relationship between microstructure and mechanical behavior in a Ti-43.5Al-4Nb-1Mo-0.1B alloy after two different heat treatments was investigated. One of the analyzed microstructures consisted of lamellar γ-TiAl/α2-Ti3Al colonies with a small volume fraction of globular γ-TiAl and β0-TiAl grains at their grain boundaries, whereas the second microstructure basically exhibited the same arrangement of the microstructural constituents, but a fraction of the lamellar colonies was altered by a cellular reaction. The prevailing microstructures have been analyzed by means of scanning electron microscopy and transmission electron microscopy. Macro-and micro-hardness measurements as well as room temperature tensile tests have revealed that the sample with both cellular and lamellar features show lower yield stress and hardness than the ones exhibiting undisturbed lamellar microstructures. The strength and hardness properties are primarily connected to the lamellar spacing within the colonies, where strength increases with decreasing lamellar spacing. The appearance of a cellular reaction leads to a refinement of the lamellar colonies which in turn influences positively the plastic fracture strain at room temperature.

Original languageEnglish
Pages (from-to)703-708
Number of pages6
JournalInternational Journal of Materials Research
Volume102
Issue number6
DOIs
StatePublished - 2011

Keywords

  • Intermetallics
  • Mechanical properties
  • Microstructure
  • Titanium aluminides

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