Effect of ZrB2 addition on microstructure evolution and mechanical properties of 93 wt.% tungsten heavy alloys

Abstract

Abstract In this study, 93\xa0wt.% tungsten heavy alloys reinforced with highly uniform and dispersed ZrO2 particles were successfully manufactured by powder metallurgy method. In order to fabricate fine-grained tungsten heavy alloys with outstanding performances, ultrafine 93W-4.9Ni-2.1Fe composite powder fabricated using a two-step reduction approach was selected as raw material. Microstructure and mechanical properties were experimentally examined to investigate the influence of ZrB2 addition. Meanwhile, transmission electron microscope and energy spectral analysis identified that ZrO2 particles were generated through the reaction between ZrB2 and oxygen from the grain boundaries. The ultimate tensile strength, elongation, and hardness of 93W-0.75ZrB2 alloys could reach to 963\xa0±\xa016\xa0MPa, 18.4\xa0±\xa01.3% and 387.6\xa0±\xa04.4 HV, respectively, benefitted from the combination of fine-grained strengthening and oxide dispersion strengthening mechanisms. The W grains without observable texture were homogeneously distributed in the γ matrix phase based on electron back-scattered diffraction analysis. Moreover, it was determined that the main fracture types of 93W-ZrB2 alloys were W grain cleavage failure and ductile matrix rupture, closely related to the ZrB2 content in alloys. The current work provided a possible method for purifying the boundaries and enhancing the strength and elongation of W-Ni-Fe alloys simultaneously.