Microstructural evolution and hydrogen content and their effect on properties of TiB2/Al-Li-X composites with different Li contents

The content and proportions of the major solute elements in aluminum matrix composites are critical to the microstructure and properties of the material. This paper uses a stepwise method based on ultrasonic in-situ casting technology to prepare TiB2/Al-Li-X composites with different Li contents (0.5-3.0 wt%). The composites' microstructure morphology, precipitates, hydrogen content, and mechanical properties were tested and analyzed. The results showed that with the increase of Li content, the number of theta ' phases decreases, the number of delta ' phases increases, while the number of T1 phases increases and then decreases, and the TiB2 particles promote the precipitation of T1 phases at low Li content; meanwhile, the hydrogen content keeps increasing, and the grain size decreases and then increases. The increase of the T1 phase and the decrease of grain size enhance the strength of the composites, while the increase of delta ' phase and hydrogen content increase the hardness but decrease the plasticity. When the Li content is around 1.5 wt%, the grain size is minimized, the TiB2 particles are fine and dispersed, the yield strength reaches the maximum value of 166.9 MPa, and the mechanical properties are relatively balanced.