Constitutive Model and Microstructure Evolution of Ti65 Titanium Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Understanding the hot deformation behavior of Ti65 alloy is crucial for optimizing manufacturing processes.
• Ti65 alloy with a bimodal microstructure exhibits complex deformation mechanisms under varying thermal-mechanical conditions.

Purpose of the Study:

• To investigate the hot deformation behavior and mechanisms of Ti65 alloy with a bimodal microstructure.
• To establish and compare the predictive accuracy of Arrhenius and Grey Wolf optimization-neural network with back propagation (GWO-BP) models for flow stress.
• To elucidate the microstructural evolution and deformation mechanisms during hot working.

Main Methods:

• Isothermal compression experiments were performed on a Thermecmastor-Z simulator.
• Temperatures ranged from 950 to 1110 °C, and strain rates ranged from 0.01 to 10.0 s^-1.
• Constitutive models (Arrhenius and GWO-BP) were developed and validated against experimental data.

Main Results:

• The GWO-BP model demonstrated higher prediction accuracy than the Arrhenius model in the two-phase region.
• Flow stress exhibited greater softening in the two-phase region compared to the single-phase region.
• Microstructural evolution included lamellar α phase transformation to globularized topography via boundary-splitting, and varying recrystallization mechanisms (discontinuous dynamic recrystallization at high strain rates).

Conclusions:

• The GWO-BP model offers superior flow stress prediction for Ti65 alloy in the two-phase region.
• Deformation mechanisms are strain-rate and phase-dependent, involving spheroidization and different types of recrystallization.
• The findings provide insights for controlling microstructure and properties during hot working of Ti65 alloy.