Dislocation-mediated tunable toughness in duplex phase tungsten heavy alloys

Tungsten heavy alloys (WHAs) with honeycomb architectures present a potential avenue to circumvent the intrinsic low-temperature brittleness of body-centered cubic tungsten (W), yet the fundamental toughening mechanisms induced by their intricate duplex phase microstructure remain intriguing. In this study, we employed small punch test to explore the deformation characteristics of 93W–4.9Ni–2.1Fe (93 W) alloys over a broad temperature range, and uncovered the dislocation-mediated tunable toughening mechanisms. At low temperature (–60 °C), prolific dislocation nucleation in γ (Ni–Fe–W) phase effectively arrests crack propagation, compensating for tungsten's inherent deficiency in dislocation nucleation and endowing 93 W alloys with exceptional low-temperature toughness. In contrast, during intermediate-temperature deformation (80–300 °C), coordinated deformation of W particles is enhanced, while the interlocking of planar-slip dislocations leads to strain localization and preferential cracking of γ phase, which degrades the toughness of 93 W alloys. Interestingly, pre-rolling induces a toughness crossover: although pre-existing dislocations harden the γ phase and diminish low-temperature cracking resistance, they facilitate strain redistribution through interfacial plasticity transfer between the duplex phases, thereby suppressing shear localization and enhancing the mid-temperature toughness of 93 W alloys. These findings offer novel strategies for tuning the performance and reliability of WHAs in a wide range of applications.