Manufacturing of Ti–Nb–Cr–V–Ni high entropy alloy using directed energy deposition and evaluation of materials properties

Abstract

High entropy alloy (HEA) is a new material that can overcome the limitations of the physical properties of conventional materials, exhibit excellent mechanical properties, and be employed in various extreme environments. In particular, refractory HEA composed of refractory materials such as Ti and Ni are expected to exhibit desirable high-temperature properties. Metal additive manufacturing has a shorter manufacturing time than the conventional casting method and is suitable for HEA manufacturing using various metal materials. Specifically, directed energy deposition (DED) has a high solidification rate that is advantageous for grain refining, prevents intermetallic compounds, and averts shrinkage that occurs in the casting method, thereby reducing cracks and deformations and resulting in fewer defects and superior production quality. In this study, a HEA with desirable high-temperature characteristics that are composed of Ti–Nb–Cr–V–Ni was designed by optimizing thermodynamic parameters and deposited using DED. The deposited Ti–Nb–Cr–V–Ni exhibited a body-centered cubic structure. Tensile strength, hardness, differential scanning calorimetry (DSC), and thermal conductivity analyses were performed to analyze its mechanical and thermal properties. Ti–Nb–Cr–V–Ni exhibited a fine structure and high tensile strength at high temperatures due to the characteristics of the DED process, but low elongation at room temperature. These strength characteristics are attributed to the microstructure of Ti–Nb–Cr–V–Ni, which mainly forms the BCC phase. And Ti–Nb–Cr–V–Ni exhibited high hardness and high thermal stability enough to be used in extreme environments with high temperatures.