Composition redistribution-induced dynamic failure of dual-phase 90W-Ni–Fe alloy during adiabatic shear localization process

With the upgrade of armor protection materials, higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles, and the penetration performance is closely related to the adiabatic shear band under extreme stress conditions. Here, the detailed analysis of the adiabatic shear band microstructure evolution of a dual-phase 90W-Ni–Fe alloy under a high strain rate was conducted by combining advanced electron microscopic characterization, while discussing shear fracture from a mechanical perspective under thermoplastic instability. The high temperature and high stress environment inside the adiabatic shear band led to the refinement of the W phase and γ-(Ni, Fe) phase grains to the submicron level, and induced the elements redistribution of W, Ni, and Fe to precipitate W nanocrystalline with hardness as high as 11.7 GPa along the recrystallization grain boundaries of the γ-(Ni, Fe) phase. Mechanical incompatibility caused by the hardness difference between W nanocrystalline and γ-(Ni, Fe) phases led to a strain gradient at the interface. The microvoids preferentially nucleated at the W nanocrystalline/γ-(Ni, Fe) phase interface, then merged to form microcracks and grew further, leading to shear failure.