Mechanical Behavior of Electron Beam Powder Bed Fusion Additively Manufactured Ti6Al4V Parts at Elevated Temperatures

Abstract

Ti6Al4V is one of the vital metal alloys used in various industries including aerospace, especially at high-temperature applications, because of having high strength-to-weight ratio, and high melting temperature. Manufacturing these metal parts by the conventional subtractive methods have been challenging due to the difficulty involved with the cutting and machining it. However, additive manufacturing (AM) offers a convenient way for shaping this metal into the desired complex parts. Although different powder bed fusion (PBF) AM processes are time and cost effective, degradation of mechanical properties during high-temperature applications could be a concern for parts produced by them. Therefore, this study focuses on the anisotropic and high-temperature elastic and plastic behaviors of Ti6Al4V parts made using electron beam powder bed fusion (EB-PBF) process. Mechanical properties, like modulus of elasticity, 0.2% yield strength, ultimate tensile strength (UTS), and percent elongation, have been determined at 200 °C, 400 °C, and 600 °C temperatures from the samples produced in different build orientations. Considerable anisotropic behavior and temperature dependency were observed for all the analyzed properties. At 600 °C, various softening mechanisms such dislocation glide, grain boundary slip, and grain growth were anticipated to be activated reducing the flow stress and increasing the elasticity. Fractography analysis on fractured surfaces of the samples reveals various defects, including partially melted or unmelted powder particles near the surface and subsurface areas. Those internal and external defects are analyzed further using X-ray computed tomography (CT) and surface profilometer to show their effect on the anisotropic behaviors.