Dynamic recrystallization induced adiabatic shear failure of dual-phase 93W-4.9Ni-2.1Fe alloy during high-speed dynamic loading

Abstract

Adiabatic shear failure is the key mechanism for the “self-sharpening” effect of tungsten alloy kinetic energy penetrators during high-speed penetration. This process involves complex mechanical responses and significant microstructural evolution, which have a decisive impact on the penetration performance of armor-piercing projectiles. This study investigates the adiabatic shear failure mechanism of 93W-4.9Ni-2.1Fe (93W) alloy under high-speed dynamic loading conditions by examining its mechanical properties and microstructural changes. Experimental findings show that the 93W alloy exhibits significant strain-rate hardening, with its yield strength increasing dramatically from 643 MPa (0.001 s⁻¹) to 2030 MPa (6000 s⁻¹). Under high-speed dynamic loading, when the strain reaches 50 %, the deformation mode transitions from uniform plastic deformation to localized shear deformation, resulting in the formation of adiabatic shear bands. During this process, the deformation mechanism of the γ-(Ni,Fe) phase changes from dislocation slip to twinning, while W particles retain dislocation slip as the primary deformation mode. When the strain reaches 70 %, the temperature within the adiabatic shear band reaches 1565 K, inducing dynamic recrystallization of the 93W alloy via a rotation mechanism. Stress concentration causes microvoids to preferentially nucleate at the recrystallized grain boundaries of W particles within the adiabatic shear band, which subsequently coalesce into microcracks. These microcracks propagate along the W/γ-(Ni,Fe) phase interfaces, ultimately leading to adiabatic shear failure of the 93W alloy.