Investigation of microstructure and crack formation for in-situ fabricated TiAl alloy by twin-wire electron beam manufacturing

TiAl intermetallics have emerged as a promising high-temperature material in the aerospace industry, distinguished by their low density and exceptional high-temperature performance. However, the inherent brittleness of this alloy has posed formidable challenges in traditional processing techniques, thereby curbing its widespread adoption. The advent of wire-based in-situ additive manufacturing (AM) technology has recently introduced a novel paradigm for fabricating traditionally brittle multi-element alloys. In this study, we harness the twin-wire in-situ AM technology for the in-situ synthesis of TiAl alloy, utilizing pure-Ti wire and pure-Al wire as the raw materials. Our investigation delves into the composition distribution, microstructure, mechanical properties, and the evolution of temperature and stress fields pertinent to solidification and cracking behavior. The results reveal that the Ti-48Al (at%) alloy, characterized with no obvious composition uniformity, can be successfully fabricated using this method. The as-printed TiAl alloy exhibits a typical interdendritic and dendritic γ-phase structure, with minimal α-phases present. Furthermore, it demonstrates a well compressive properties of 1841±148 MPa on average. Stress concentration primarily manifests at the ends of the deposition part and the midpoint of the component during the initial layers' printing process, rendering these locations susceptible to crack formation. This study holds significant implications not only for advancing the dual-wire AM methodology but also for accelerating the industrial application of TiAl alloy in the aerospace industry.