A Finite Element Analysis-Based Digital Twin for Investigating the Mechanical Behavior of Ti–6Al–4V at High and Moderate Temperatures
Authors: Xu Dong , Frame Lesley D. , Kim Jeongho , Tang Jiong 
Published: January 2025

Abstract
The titanium alloy Ti-6Al-4V is widely used across various applications, such as aircraft structural components, machinery parts, and particularly in parts for medical devices. Understanding the deformation behavior and microstructural changes of this material during thermal processing is essential for achieving the required product dimensions and ultimate mechanical properties. The transformation of Ti-6Al-4V’s crystal structure from the beta phase (body-centered cubic structure) to the alpha phase (hexagonal close-packed structure) occurs over a temperature range of 980°C to 650°C. Therefore, investigating the mechanical behavior of Ti-6Al-4V within this temperature spectrum is crucial for optimizing the heat treatment process and improving the alloy’s mechanical properties. Existing studies have revealed that in this temperature range, the increase in flow stress of Ti-6Al-4V as the temperature decreases exhibits a unique non-linear behavior. Utilizing a Finite Element Analysis (FEA)-Based Digital Twin enables precise simulations of complex behaviors, offering deep insights into stress distribution and deformation patterns under various thermal conditions. This predictive model plays a crucial role in enhancing heat treatment methodologies, crafting components with improved mechanical properties, and reducing both the cost and time associated with experimental procedures.
The utilization of the Gleeble 3500 physical simulator emerges as a cornerstone in this study for the systematic collection of experimental data, specifically targeting a range of predefined temperatures and strain rates. This investigation notably pioneers the use of a variable temperature tensile test, a methodological innovation aimed at an in-depth exploration of the phase transformation dynamics inherent to the Ti-6Al-4V alloy. This technique is distinguished by its gradual temperature reduction strategy, enabling a nuanced analysis of thermal effects on material properties. In the realm of high-temperature alloy research, empirical constitutive models, particularly the Johnson-Cook constitutive relationship, have traditionally served to model the mechanical behaviors of metals subjected to high-temperature environments and varying strain rates. However, a critical analysis reveals that the Johnson-Cook model simplistically predicts temperature-induced flow stress variations in a linear manner, a representation that falls short of capturing the complex behaviors observed in real-world applications. To address this discrepancy, the current research advances a “Modified Johnson-Cook” model, an adaptation specifically formulated to capture the intricate non-linear flow stress variations observed in the Ti-6Al-4V alloy. This refinement is pivotal in accurately characterizing the alloy’s response to thermal processing. To operationalize this enhanced model, a Fortran code was meticulously developed, enabling its integration into finite element analysis workflows. This technological integration marks a significant stride towards achieving a comprehensive and precise representation of the Ti-6Al-4V alloy’s mechanical behavior under a spectrum of thermal conditions, spanning from moderate to elevated temperatures. This advancement underscores the study’s contribution to the field, potentially guiding the optimization of heat treatment processes and material design strategies for high-temperature applications.