COMPUTER AIDED ENGINEERING FOR THERMO-MECHANICAL-METALLURGICAL ANALYSIS OF FORGING OPERATIONS OF TITANIUM ALLOYS

In this thesis a study on the forging processes of Ti-6Al-4V titanium alloy, with particular focus on the numerical applications and simulation design of hot forming methods, was done. The aim of this work is to collect all data concerning the material definition in terms of thermal, mechanical and microstructural properties of the selected alloy in order to filter all useful information to describe the behavior of the material under the characteristic conditions of the hot forging processes, taking into account both thermo-mechanical and metallurgical aspects involved during a such complex thermo-mechanical stage. Those information were collected and used to characterize the material properties, creating a first coupled characterization for the considered material with the aim of link both thermal-mechanical and thermal-microstructural behaviors in running numerical analysis of hot forging processes. The collected data was validated by means of comparison with a forging campaign of workpieces for aeronautical applications involved within the research project Titaform, which had the objective to study and determine a methodic design approach in set-up of precision hot forging of titanium alloys. After the first validation, all collected information were used to develop a self-consisten system based on the Johnson-Cook equation with the aim of creating a fully coupled constitive model for multiphasic titanium alloys which takes into account both thermal, mechanical and microstructural properties as function of field variables. The final objective considers the thermo-mechanical behavior of each main phase of Ti-6Al-4V alloy in order to carry out the contribution of each allotropic form during a non-isothermal deformation. Results showed a good agreement with experimental observations.