Improved fracture behavior and microstructural characterization of heterogeneous-structured tungsten

Tungsten and its alloys are known to be brittle at room temperature and have high ductile-to-brittle transition temperatures. Improving the ductility of tungsten has significant impact on the range of applications. Here, we report a kind of heterogeneous-structured pure tungsten, which shows an improved ductility. The heterogeneous-structured tungsten is produced by hot-rolling and partial recrystallization of pure tungsten. The structural heterogeneity is composed by elongated grains with a high density of low angle grain boundaries and blocky regions of recrystallized grains. The fracture behavior is systematically studied on the heterogeneous-structured tungsten, which shows that the path of crack propagation plays an important role on improving the ductility. Trangranular fracture is the preferred crack path in the banded regions with elongated grains and intergranular fracture dominates the crack propagation when the crack extends to the blocky recrystallized grains. The cooperation of trangranular and intergranular fracture modes increases the total work to fracture and thus improves the ductility. This study is instructive for the development of advanced high-performance pure tungsten with good mechanical properties.