• Coelho, R. S.
• Schell, N.
• Pinto, H. C.
• Wu, L.
• Callegari, B.
• Aristizabal, K.
• Soldera, F. A.
• Brito, P. P.
• Oliveira, João Pedro
• Mücklich, F.

Abstract

The aging behavior of a Ti-6Al-4V alloy with different starting microstructures was evaluated by means ofsynchrotron X-ray diffraction, scanning-transmission electron microscopy and micro-hardness measurements.Initial microstructures were produced by thermal and thermomechanical treatments and comprised differentmorphologies of α phase (martensitic, lamellar, bimodal and globular), as well as the presence or absence of theβ phase. Results show that one or more of the following phenomena can take place during aging and contributeto the hardening of the alloy: β decomposition into fine secondary α laths; transformation of the metastablemartensitic α′ into the equilibrium α phase; and precipitation of the intermetallic Ti$_3$Al. The composition anddistribution of the β phase was shown to affect the precipitation of secondary α during aging, while the compositionof the α phase plays a key role on the formation of Ti$_3$Al. In situ X-ray diffraction studies of the earlystages of aging show the kinetics of the α′→α conversion by the reduction in FWHM of XRD reflections, indicatethe contribution to hardening by the increase of the c/a ratio and the consequent limitation of active slip systemsand depict the chemical homogenization and decomposition of the β phase.

Topics

• microstructure
• phase
• x-ray diffraction
• hardness
• transmission electron microscopy
• precipitation
• aging
• intermetallic
• homogenization
• decomposition
• aging