Ultra-cryogenic and room temperature normalized impact toughness of laser additively manufactured Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr

Titanium alloys represent key materials in aviation due to their high strength-to-weight ratio and corrosion resistance. With the transition toward carbon-neutral aviation, hydrogen-powered engines are expected to play a central role in short- and medium-range operations. The implementation of such technologies requires the development of liquid hydrogen storage and distribution systems, which in turn demands a thorough understanding of the ultra-cryogenic performance of the materials. In this context, the impact toughness represents a critical parameter for assessing material failure. At the same time, additive manufacturing is gaining increasing relevance for aerospace applications, offering unprecedented design freedom. Therefore, for the first time, two different additively manufactured standard titanium alloys (Ti-6Al-4V, Ti-5Al-5Mo-5V-3Cr) were analyzed regarding their normalized impact toughness ( K C ) at room temperature and under a constant ultra-cryogenic temperature of 20 K with in-situ cooling, being equivalent to the temperature of liquid hydrogen (LH₂), revealing different fracture mechanism despite similar K C . In this context, the influence of a hot-isostatic pressing treatment as well as variation of printing process parameters were considered. Higher volumetric energy densities used for additive manufacturing of Ti-6Al-4V, lower the K C . Moreover, the K C for this material is slightly higher at 293 K than at 20 K. Ti-6Al-4V has higher K C than Ti-5Al-5Mo-5V-3Cr at 293 K and 20 K. Ti-5Al-5-Mo-5V-3Cr additionally revealed nearly the same K C in hot-isostatic pressed and as-built condition at 293 K, but higher value for the hot-isostatic pressed condition at 20 K compared to 293 K.