Enhanced mechanical properties of tungsten alloy by synergistic strengthening of flaky Ni3Al and Al2O3 nano-particles

Abstract

Tungsten alloys are extensively applied in kinetic energy penetrators but these alloys exhibit poor self-sharping properties—connected with high thermal conductivity, large grain size, and low hardness—which limit their application. Ni3Al is one of the most promising candidates as a binder phase for tungsten alloys used as kinetic energy penetrators because of its high hardness, low thermal conductivity, and low solubility of tungsten, which can refine the tungsten grain. In this study, a simple and scalable methodology, termed ‘synergistic strengthening with flaky binder phase and ceramic nano-particles’, has been developed to fabricate high-performing W-Ni3Al alloys. The flaky Ni3Al binder phase acted as a ductile layer to improve the mechanical properties of the alloy by crack deflection and tip blunting. The in-situ formed nano Al2O3 particles on the interface between the W and Ni3Al phase inhibited the dislocation motion and restrained the dissolution and re-precipitation of the tungsten grain, leading to grain refining of the tungsten and alloy strengthening. As a result, a unique structural W-Ni3Al alloy was prepared with an approximately 2 µm tungsten grain size, and its bending strength was improved by 24.3% in comparison to conventional W-Ni3Al alloys, and the hardness of greater than 70 HRA remained constant. Moreover, it was exciting that the higher bending strength could be obtained by regulating the W-Ni3Al alloy microstructure. In short, we demonstrated that this structural design strategy was an effective method to fabricate refractory alloys, such as tungsten alloys, with good overall mechanical performance.