Effect of ZrB2 addition on microstructure and mechanical properties of 95W-HEA alloys

In tungsten heavy alloys, the substitution of conventional binders with novel high entropy alloys and the addition of rare metal borides have demonstrated considerable promise in enhancing comprehensive performance. In this study, 95W-5CoCrFeNiMn-x ZrB2 (x = 0.1, 0.2, 0.4, 0.6, 0.8) was synthesized by powder metallurgy method and characterized. The results show that: the spherical tungsten grains are distributed in binder network, and the added ZrB2 reacts with oxygen to generate ZrO2 and B2O3, which will affect the microstructure and properties of the alloys. An increase of ZrB2 content results in a reduction in alloy density, accompanied by an enhancement in hardness; the changes in grain size, contiguity, and solid volume fraction present a trend of first falling and then rising, and the minimum value is obtained when the addition is 0.4 wt%. At this time, 95WHEAs-0.4 ZrB2 presents the best comprehensive performance, exhibiting an average grain size of 16.80 mu m, a relative density of 96.10 %, a hardness of 411.68 HV1, and a compressive strength of 2457.64 MPa. The primary fracture mode observed in the alloys is W-binder interfacial separation, with a minor occurrence of tungsten cleavage when the ZrB2 addition is within an optimal range.