Microstructure and mechanical properties of nano TiB whisker-reinforced titanium matrix composites using atomized Ti–TiB composite powder as raw materials

Abstract

In situ formed TiB-reinforced titanium matrix composites (TMCs) have gained significant attention for their high specific modulus and strength. However, the high sintering temperatures required for in situ reactions and densification can cause rapid coarsening of TiB whiskers, limiting the improvements in mechanical properties. This study proposes a "low-temperature sintering + hot extrusion" method to prepare nano TiB-reinforced Ti–TiB composites. The process involves low-temperature sintering at 800 °C—below the HCP-Ti phase transformation temperature—followed by hot extrusion for densification. The resulting Ti–TiB composites feature TiB with diameters of approximately 123 nm. The yield strength (YS) and ultimate tensile strength (UTS) of the nano TiB-reinforced Ti–TiB composites reach 632 MPa and 833 MPa, respectively, reflecting increases of 70 % and 51 % compared to microscale TiB-reinforced Ti–TiB composites, while maintaining an elongation (El) of 13.97 %. The size evolution of TiB in the composites follows a temperature-dependent progression. Below 800 °C, TiB remains nanoscale, while temperatures above 800 °C, TiB grows to the microscale. The failure mode also shifts with TiB size, from interfacial debonding at the microscale to load-bearing fracture at the nanoscale. Additionally, the refinement of matrix grains and the obstruction of dislocations by nanoscale TiB further improve mechanical properties. This work opens a new controllable and facile route for preparing nano TiB-reinforced titanium matrix composites with promising properties.