Tungsten materials with high strength double nanostructure have been successfully prepared in China

       Recently, the research group of Fang Qianfeng, Institute of solid physics, Hefei Institute of material science, Chinese Academy of Sciences has made important progress in the research and development of nanostructured tungsten based alloys. High strength dual nanostructured tungsten materials have been successfully prepared by pressure assisted low temperature densification sintering. Relevant work was published in International Journal of refinery metals and hard materials.

Tungsten based alloys are considered to be the most potential plasma facing first wall materials for fusion reactors in extreme environments, but the brittleness of commercial pure tungsten greatly limits their application. Oxide dispersion strengthening (ODS) is one of the effective ways to improve the toughness of W-based alloy, but the oxide particle size in ods-w is large, which can not reach the ideal strengthening and toughening effect. In order to solve this problem, the researchers used the experience of solid solution precipitation mechanism in ODS Fe to control the oxide particle size below 3nm, and successfully prepared the double nanostructured tungsten materials by pressure assisted low-temperature densification sintering: W grain size ~ 67nm and y2ti2o7 oxide particle size ~ 10nm.

Firstly, Y2O3 and Ti are "solid solution" into w matrix by high-energy ball milling, and then w-1.0% y2o3-0.7% Ti powder after high-energy ball milling is densified and sintered by spark plasma sintering (SPS) technology. By strictly controlling the sintering temperature, y2ti2o7 nanoparticles are precipitated and evenly distributed in the tungsten matrix. These fine second phase nanoparticles inhibit tungsten crystal Finally, the preparation of w-1.0% y2o3-0.7% Ti bulk alloy was realized. The results of XRD and TEM show that the average size of W grain is 67nm, and the average size of oxide grain in the crystal and grain boundary is 8.5nm and 16.4nm, respectively, as shown in the figure. The micro Vickers hardness of the nano structure W alloy is up to 1441 HV, which is 2-3 times higher than that of the common W alloy reported in the literature. The extremely high microhardness is due to the synergistic strengthening effect of nanometer W grains and uniformly dispersed nanometer oxide particles. This solid solution precipitation process provides a general way for the preparation of nanocrystalline refractory metals by controllable dispersion of nano oxides.

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