Creep mechanisms vis-à-vis power law vs. grain boundary sliding in α-β titanium alloys for physics based prognostics

Abstract

This work is performed in support of our continued physics-based prognostics system development using a life cycle management-expert system (LCM-ES) framework. The physical damage based modeling approach involving global behavior and localized response of a component at the microstructural level is used. The current research aims at constructing parts of a deformation mechanism map (DMM) for α-β Ti alloy. The appropriate constitutive equations are used for power law creep and grain boundary sliding mechanisms. Simulations are performed using the Newton-Raphson method using Matlab software code in order to obtain contour lines corresponding to strain rates ranging from 104 to 10-12 over the homologous temperature ranges of 0.10 to 0.655. The dominance of power law creep and grain boundary sliding over a wider range of stresses and temperatures in Ti-64 alloy is studied. The simulation results are validated using experimental data points. The predicted contour lines in the map match fairly well. The structure-creep mechanism relationships in α-β Ti alloy under different stress, temperature and strain rate conditions are discussed.