materials Article Thermo-Mechanical Modeling of Wire-Fed Electron Beam Additive Manufacturing Fatih Sikan 1,2 , Priti Wanjara 2 , Javad Gholipour 2 , Amit Kumar 1 and Mathieu Brochu 1, *   Citation: Sikan, F.; Wanjara, P.; Gholipour, J.; Kumar, A.; Brochu, M. Thermo-Mechanical Modeling of Wire-Fed Electron Beam Additive Manufacturing. Materials 2021, 14, 911. https://doi.org/10.3390/ ma14040911 Academic Editor: Mika Salmi Received: 8 January 2021 Accepted: 3 February 2021 Published: 15 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by National Re- search Council of Canada. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecom- mons.org/licenses/by/ 4.0/). 1 Department of Materials Engineering, McGill University, Montreal, QC H3A 0C5, Canada; fatih.sikan@mail.mcgill.ca (F.S.); amit.kumar2@mail.mcgill.ca (A.K.) 2 National Research Council Canada, Aerospace Research Center, Montreal, QC H3T 2B2, Canada; priti.wanjara@cnrc-nrc.gc.ca (P.W.); javad.gholipourbaradari@cnrc-nrc.gc.ca (J.G.) * Correspondence: mathieu.brochu@mcgill.ca Abstract: The primary objective of this research was to develop a finite element model specifically designed for electron beam additive manufacturing (EBAM) of Ti-6Al-4V to understand metallurgical and mechanical aspects of the process. Multiple single-layer and 10-layer build Ti-6Al-4V samples were fabricated to validate the simulation results and ensure the reliability of the developed model. Thin wall plates of 3 mm thickness were used as substrates. Thermocouple measurements were recorded to validate the simulated thermal cycles. Predicted and measured temperatures, residual stresses, and distortion profiles showed that the model is quite reliable. The thermal predictions of the model, when validated experimentally, gave a low average error of 3.7%. The model proved to be extremely successful for predicting the cooling rates, grain morphology, and the microstructure. The maximum deviations observed in the mechanical predictions of the model were as low as 100 MPa in residual stresses and 0.05 mm in distortion. Tensile residual stresses were observed in the deposit and the heat-affected zone, while compressive stresses were observed in the core of the substrate. The highest tensile residual stress observed in the deposit was approximately 1.0 σ ys (yield strength). The highest distortion on the substrate was approximately 0.2 mm. Keywords: thermo-mechanical modelling; finite element analysis; residual stresses; microstructure; Ti-6Al-4V 1. Introduction In recent years, additive manufacturing (AM) technologies have revolutionized the manufacturing industry due to their original layer-by-layer processing nature and known advantages over conventional forming, forging, casting, and/or machining technologies [1]. Currently, AM is used to produce custom parts from a vast selection of materials in many industries, such as aerospace [2], automotive [3], satellite and space [3], and biomedical [4]. The main reasons for AM attracting such attention are (1) the potential of complex shape fabrication, design freedom to highlight creativity and part uniqueness [5], and (2) promis- ing sustainability through cost effectiveness by decreasing lead time, production waste of high cost materials, energy consumption, and, thus, overall cost per part [6]. Despite several advantages, AM technology also has limitations that need to be addressed prior to becoming a mainstream production method, especially for critically loaded structures [7]. Production, geometry, and microstructural issues—such as porosity, lack of fusion between layers [8], cracking and distortion due to thermal and residual stresses [9], low spatial resolution in the final shape [10], high surface roughness [11], or need for post-processing (such as heat treatments, surface treatments, thermo-mechanical treatments or machining) [12]—hinder the advancement of AM in many fields. Such engineering challenges cause massive issues for strategic and critical industries such as aerospace where part requirements are very stringent for safety and reliability assurance. In addition, current materials used to build metal parts with AM are quite limited, and the Materials 2021, 14, 911. https://doi.org/10.3390/ma14040911 https://www.mdpi.com/journal/materials