An Analysis on the Constitutive Models for Forging of Ti6Al4V Alloy Considering the Softening Behavior

Abstract

This paper developed high-temperature deformation constitutive models for a Ti6Al4V alloy using an empirical-based Arrhenius equation and an enhanced version of the authorsÕ physical-based EM + Avrami equations. The initial microstructure was a partially equiaxed a + b grain structure. A wide range of experimental data was obtained from hot compression of the Ti6Al4 V alloy at deformation temperatures ranging from 720 to 970°C, and at strain rates varying from 0.01 to 10 s 21 . The friction-and adiabaticcorrected flow curves were used to identify the parameter values of the constitutive models. Both models provided good overall accuracy of the flow stress. The generalized modified Arrhenius model was better at predicting the flow stress at lower strain rates. However, the model was inaccurate in predicting the peak strain. In contrast, the enhanced physical-based EM + Avrami model revealed very good accuracy at intermediate and high strain rates, but it was also better at predicting the peak strain. Blind sample tests revealed that the EM + Avrami maintained good predictions on new (unseen) data. Thus, the enhanced EM + Avrami model may be preferred over the Arrhenius model to predict the flow behavior of Ti6Al4V alloy during industrial forgings, when the initial microstructure is partially equiaxed.

Improved Predictability of Microstructure Evolution during Hot Deformation of Titanium Alloys

“…The values of the activation energy ( ), , , and that define the yield stress of the α- and β-phases are listed in Table A5 . A detailed procedure for the parameter calculation was published elsewhere [ 59 ]. For both alloys, the parameters of the yield stress of the β-phase are obtained by fitting the measured yield stress in the β-domain with Equation (A17).…”

“…A simple approach is considered to calculate the yield stress assuming an Arrhenius-type behavior (Equation (A17)) [ 59 ]. where is the strain rate, is the universal constant of gases (8.314 J.mol −1 .K −1 ) and the temperature.…”

“…For the iso-stress regime, the flow stress of the β-phase is equal to the flow stress for the α-phase. The strain rates in the α- and β-phases are calculated by Equation (A21) [ 59 ] and Equation (A22), respectively. …”

Dislocation Density–Based Model and Stacked Auto‐Encoder Model for Ti‐55511 Alloy with Basket‐Weave Microstructures Deformed in α + β Region

“…Lin et al [21] established the strain-compensated Arrhenius equations, Hensel-Spittel, and intelligent algorithm models to study the flow behaviors of the Ti-5Al-5Mo-5V-1Cr-1Fe alloy and revealed that the intelligent algorithm models can preferably explain the complex flow behaviors. Souza et al [46] established accurate constitutive models to simulate the forging process of a Ti-6Al-4V alloy. Bobbili and Madhu [47] compared the prediction accuracies of the artificial neural network (ANN) model, modified Khan-Huang-Liang (KHL) model, and modified Johnson-Cook (J-C) model for a biomedical Ti alloy.…”

Precipitation of Secondary Phase and Phase Transformation Behavior of a Solution‐Treated Ti–6Al–4V Alloy during High‐Temperature Aging

“…In addition, the phase transformation behaviors have remarkable effects on the mechanical performances of titanium alloys . Some literatures have reported that the transition phases, such as α′, α″, and ω phases, often appear during aging heat treatment .…”