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

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 alpha phase tends to first precipitate from the beta matrix at low temperature (for example at 400 degrees C) till the precipitation product becomes fully alpha 2 phase at 500 degrees C or above. The transformation of beta phase into alpha 2 phase follows an orientation relationship: {0001}alpha 200{011}beta and {1120}alpha 200{111}beta, and the transformation is highly temperature and time dependent. The precipitation kinetics is the fastest at 500 degrees C. The upper temperature for alpha 2 phase to precipitate is around 800 degrees C. The heat treatment significantly influences the mechanical properties. A strength as high as 1750 MPa is obtained in the sample annealed at 500 degrees C for 6 h.