Synergistic improvements in mechanical and thermal performance of TiB2 solid solution-based composites

Continuously strengthening the mechanical properties of ultra-high temperature ceramics (UHTCs) is the future requirement. However, the mechanical properties of classical UHTCs HfB2 and ZrB2 are not satisfactory among transition metal light elements (TMLEs) compounds. TiB2 has superior mechanical properties compared to both HfB2 and ZrB2, but has inherent brittleness and limited oxidation resistance. In this work, a low content of solution strengthening was used to fabricate dense samples of Tix(Hf/Zr)1-xB2 (THZ) under high pressure and high temperature (HPHT). Compared to pure TiB2, Ti0.94(Hf/Zr)0.06B2 exhibits a significant increase of 38.8 % in oxidation resistance temperature (950 ℃) while Ti0.91(Hf/Zr)0.09B2 shows a notable increase of 28 % in fracture toughness (5.8 MPa·m0.5). Synergistic effect of dual-atom solid-solution results in local inner stress and anomalous lattice contraction. Finally, lattice-contraction was achieved to resist the oxygen invasion, thereby elevating the oxidation resistance threshold. Additionally, local inner stress induces crack deflection within individual grains, enhancing toughness through energy dissipation. This work provides a new strategy for fabricating robust UHTCs in TMLEs, which is significant for future applications.