Damage Tolerance of Aerospace Alloys at Cryogenic Temperatures

The decarbonisation of aviation will not be possible without exploring alternative fuels such as liquid hydrogen, and as a result, development of new fuel systems is essential. These system components require exceptional strength and toughness over large temperature ranges, reaching as low as 20 K, necessitating the exploration of strength, fracture toughness, and deformation mechanisms of current aerospace alloys at these temperatures. A series of offline and online uniaxial tensile and compact tension C(T) tests of SS321, S80 and Inconel 718 will explore how strengths and fracture toughnesses of these alloys change with temperature, as well as whether any strain- or temperature-induced phase transformations occur. Based on prior beamtime and resonant ultrasound spectroscopy data, it is expected that yield and ultimate strengths of all alloys will increase at 20 K compared to room temperature, and fracture toughness will decrease for SS321 and S80, while increasing for Inconel 718. S80 is expected to have limited strain-induced phase transformation; temperature- and strain-induced phase transformations are expected for SS321, and twinning is predicted as a deformation mechanism in Inconel 718. Such strength, fracture toughness and deformation mechanism probing has not been previously measured for SS321, S80 and Inconel 718, and as such we expect novel results offering insights into the viability of these alloys in liquid hydrogen fuel systems.