Unified modeling of flow softening and globularization for hot working of two-phase titanium alloy with a lamellar colony microstructure

• Published in: Journal of alloys and compounds Vol. 600; pp. 78 - 83
• Main Authors: Gao, Pengfei, Yang, He, Fan, Xiaoguang, Zhu, Shuai
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 05.07.2014; Elsevier
• Subjects: Constitutive relationships; Cross-disciplinary physics: materials science; rheology; Deformation, plasticity, and creep; Evolution; Exact sciences and technology; Flow stress; Kinetics; Materials science; Mathematical models; Mechanical properties; Metals and alloys; Microstructure; Physics; Strengthening; Titanium base alloys; Treatment of materials and its effects on microstructure and properties; Yield strength; Mechanical properties; Metals and alloys; Kinetics; Microstructure; Constitutive equation; Globular structure; Strengthening; Plastic flow; Hot working; Strain softening; Compressive testing; Dislocation density; Titanium alloys; Lamellar structure; Dynamic model; Hall Petch relationship
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.02.110

•Flow stress and globularization of titanium alloy with lamellar structure are molded.•Physically based model couples the constitutive behavior and microstructure change.•Globularization and Hall–Petch strengthening are considered in microstructure model.•The model can realize unified prediction of flow stress and globularization kinetics. In this paper, a set of physically based constitutive model coupling microstructure evolution was developed for unified prediction of flow stress and globularization evolution during hot working of two-phase titanium alloys with initial lamellar microstructure. The dislocation density variation, dynamic globularization and effect of Hall–Petch strengthening were considered in the microstructure model. The dynamic globularization was modeled by two parts: critical strain for initiation of globularization and globularization rate, both of which are function of processing conditions (temperature and strain rate); In the modeling of Hall–Petch strengthening, the dependence of Hall–Petch coefficient on processing conditions were considered and the loss of Hall–Petch strengthening with deformation process was molded. The microstructure model was implemented to a physically based constitutive model, composed of a thermally activated stress and an athermal stress, to realize the unified prediction of flow stress and globularization evolution. The material parameters were determined by calibration using the experimental flow stress and globularization fraction in isothermal compression tests through the genetic algorithm based optimization method. Based on the set of constitutive models, flow stress and globularization evolution of Ti–6Al–4V and TA15 alloys at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained.