Microstructure and strengthening mechanism of high-performance boron modified titanium materials prepared by selective laser melting based on low-cost modified powder

This study aims to put forward new insights into preparing high-performance titanium (Ti) materials by selective laser melting (SLM). Employing low-cost modified TiB 2 /Ti composite powder suitable for the SLM process as raw materials, boron modified titanium materials with high relative density (99.86 %), no cracking, and excellent comprehensive properties were successfully fabricated. A systematic analysis was carried out on the evolution of the matrix microstructure induced by TiB whiskers, and the strengthening mechanism of boron modified titanium materials was deliberated. During the SLM process, TiB 2 undergoes a complete in-situ reaction with the Ti matrix, precipitating nanoscale TiB whiskers with an average length of 102.0 nm, a width of 17.2 nm, and a content of 0.71 wt%. The heterogeneous nucleation and pinning effects induced by TiB whiskers result in significant refinement of grains, with the average size of titanium grains attaining 3.3 μm. After heat treatment (750 °C/2 h), the aspect ratio of TiB whiskers increases significantly (∼19.4). The room temperature ultimate tensile strength (UTS) of the boron modified titanium materials is 1103 ± 12 MPa, with an elongation (EL) of 3.9 ± 0.5 %. Following heat treatment, the room temperature UTS of the material is 995 ± 11 MPa, and the EL is 8.0 ± 0.6 %. The strengthening mechanisms introduced by TiB before and after heat treatment primarily depend on the contributions of dispersion strengthening and grain refinement strengthening, followed by solid solution strengthening and TiB load-bearing strengthening. The synergistic effect of these four mechanisms contributes to the tensile properties of boron-modified titanium materials. The results show that the size of TiB whiskers and the degree of grain refinement play a crucial role in enhancing the performance.