China Successfully Developed High-strength Double-nanostructure Tungsten Materials

Recently, the research group of Fang Qianfeng, a researcher at the Institute of Solid State Physics, Chinese Academy of Sciences, made significant progress in the development of nanostructured tungsten-based alloys, and successfully prepared high-strength dual-nanostructured tungsten materials through pressure-assisted low-temperature densification sintering. Related work is published in the International Journal of Refractory Metals and Hard Materials.

Tungsten-based alloys are considered to be the most promising plasma-facing first wall materials that can be used in the extreme environment of fusion reactors, but the brittleness of commercial pure tungsten greatly limits their applications. Oxide dispersion strengthening (ODS) is one of the effective ways to improve the toughness of tungsten-based alloys. However, the current ODS-W has a large oxide particle size and cannot achieve the desired toughening effect. In response to this problem, the researchers borrowed the experience of using ODS-Fe to control the oxide particle size below 3nm by using the solid solution-precipitation mechanism, and successfully prepared a dual-nanostructure tungsten material through pressure-assisted low-temperature densification and sintering: Particle size ~ 67nm and Y2Ti2O7 oxide particle size ~ 10nm.

Researchers first "solid solution" Y2O3 and Ti into the W matrix through high-energy ball milling, and then use spark plasma sintering (SPS) technology to densify and sinter the W-1.0% Y2O3-0.7% Ti powder after high-energy ball milling. Strictly control the sintering temperature so that nano-scale Y2Ti2O7 particles are precipitated and uniformly dispersed in the tungsten matrix. These small second-phase nanoparticles inhibit the growth of tungsten grains, and finally achieve a dual-nano structure W-1.0% Y2O3-0.7% Ti block Preparation of bulk alloy materials. XRD and TEM results show that the average size of W grains is 67nm, and the average particle diameters of oxide particles in the grains and grain boundaries are 8.5nm and 16.4nm, as shown in the figure. The micro-Vickers hardness of this nanostructured W alloy is as high as 1441 Hv, which is 2-3 times that of ordinary W alloys reported in the literature. Extremely high microhardness, resulting from the synergistic strengthening effect of nano-scale W grains and uniformly dispersed nano-oxide particles. This solid solution-precipitation process provides a general way to prepare nanocrystalline refractory metals by dispersing nanoscale oxides in a controlled manner.

This work is supported by the key R & D projects of the Ministry of Science and Technology and the National Natural Science Foundation of China.