Effect of heat treatment on microstructure and mechanical properties of Ti58Al13Nb14Zr15 medium entropy alloy

Abstract

The cautious introduction of precipitated phases is an efficient approach to optimize the microstructure and properties. In the present study, a medium entropy alloy of Ti58Al13Nb14Zr15 was annealed under different conditions to explore the microstructure and mechanical property variations. It is revealed that α phase tends to first precipitate from the β matrix at low temperature (for example at 400 ℃) till the precipitation product becomes fully α2 phase at 500 ℃ or above. The transformation of β phase into α2 phase follows an orientation relationship: {0001}α2∥{011}β and {1̅1̅20}α2∥{1̅11̅}β, and the transformation is highly temperature and time dependent. The precipitation kinetics is the fastest at 500 ℃. The upper temperature for α2 phase to precipitate is around 800 ℃. The heat treatment significantly influences the mechanical properties. A strength as high as 1750 MPa is obtained in the sample annealed at 500 ℃ for 6 h.