Improved mechanical properties of tungsten alloy by flaky Ni3Al and trace B2O3 synergistic reinforcement

Abstract

Although Ni3Al with low thermal conductivity has the advantage of being the binder phase of tungsten heavy alloys (WHAs), the reported W-Ni3Al alloy’s poor mechanical properties limit its application as the kinetic energy penetrator (KEP). In this study, low temperature sintering (B2O3 addition) and flake powder metallurgy (FPM) were combined for the first time to fabricate WHAs with excellent mechanical properties and high relative density. In the whole sintering process, the activation energy of the alloys was low. The alloys’ relative density and tungsten grain size increased as the sintering temperature raised from 1100 to 1300 °C, while their bending strength and hardness firstly increased and then decreased. For the alloy sintered at 1200 °C, massive Ni3Al flakes were perpendicular to the loading direction of SPS, bearing applied load and deflecting cracks propagation. Meanwhile, in-situ Al2O3 phase obstructed the dislocations motion during deformation. Besides, the alloy also featured tungsten grains’ bimodal distribution, no brittle phases, the ultrafine-grained Ni3Al flakes with high storage capacity for dislocations, and the well-bonded semi-coherent interface among different phases. Hence, the 1200 °C sintered alloy showed optimal properties, and its bending strength, hardness, relative density, average tungsten grain size were 1450.57 ± 19.68 MPa, 71.70 ± 0.16 HRA, 98.10 % ± 0.25%, and 3.869 ± 0.984 µm, respectively. In brief, this study provided a low-cost and simple method for the preparation of high-performance WHAs, and this low-temperature sintering combined with FPM also can be extended to the fabrication of other refractory alloys with excellent properties.