Frictional shear induced modification of the mechanical properties of TiAl(Nb) intermetallics near the surface

Mechanical properties of the two-phase TiAl(Nb) alloys have been studied after being subjected to mechanical as well as electrolytic polishing. Indentation tests at different maximum loads using different instrumentation allow probing the overall mechanical behavior of the alloys. Nanoindentation experiments have been carried out to study the local hardening of each phase during mechanical polishing. Since the deformation of γ-TiAl is facilitated by twin formation, the mechanical polishing associated with considerable frictional forces causes a significant work hardening of the γ-TiAl phase resulting in an enhancement of the overall surface hardness of the alloy. A similar hardening effect has been observed during a scratch test. The influence of local hardening owing to different crystal structures on the overall mechanical behavior in the mechanically polished alloys has also been investigated.

Research highlights▶ Mechanical properties of the two phase TiAl(Nb) alloys have been studied after being subjected to mechanical as well as electrolytic polishing. ▶ Indentation tests at different maximum loads using different instrumentation allow probing the overall mechanical behavior of the alloys. ▶ Nanoindentation experiments have been carried out to study the local hardening of each phase during mechanical polishing. ▶ Since the deformation of γ-TiAl is facilitated by twin formation, the mechanical polishing associated with considerable frictional forces causes a significant work hardening of the γ-TiAl phase resulting in an enhancement of the overall surface hardness of the alloy. ▶ A similar hardening effect has been observed during a scratch test. ▶ The influence of local hardening owing to different crystal structures on the overall mechanical behavior in the mechanically polished alloys has also been investigated.