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

Continuously improving the mechanical properties of ultra-high-temperature ceramics (UHTCs) is a key requirement for their future applications. However, the mechanical properties of conventional UHTCs, HfB₂ and ZrB₂, remain unsatisfactory among transition metal light-element (TMLE) compounds. TiB₂ has superior mechanical properties compared to both HfB₂ and ZrB₂, but suffers from inherent brittleness and limited oxidation resistance. In this work, low-content solid-solution strengthening was used to fabricate dense samples of Ti_x(Hf/Zr)_1−xB₂ (THZ) under high pressure and high temperature (HPHT). Compared to pure TiB₂, Ti_0.94(Hf/Zr)_0.06B₂ exhibits a significant 38.8% increase in oxidation resistance temperature (950 °C), while Ti_0.91(Hf/Zr)_0.09B₂ shows a notable 28% enhancement in fracture toughness (5.8 MPa⋅m^1/2). The synergistic effect of a dual-atom solid-solution results in local internal stress and anomalous lattice contraction. This lattice contraction helps resist oxygen invasion, thereby elevating the oxidation resistance threshold. Additionally, the internal stress induces crack deflection within individual grains, enhancing toughness through energy dissipation. This work provides a new strategy for fabricating robust UHTCs within TMLE systems, demonstrating significant potential for future high-temperature applications.