Microstructural characteristics and evolution mechanisms of 90W–Ni–Fe alloy under high-strain-rate deformation

Abstract

Investigations into the microstructural characteristics and evolution mechanisms of 90W–Ni–Fe alloy during deformation under high strain rates were conducted using a Split Hopkinson Pressure Bar (SHPB) system. With increasing strain rate and strain the 90W–Ni–Fe alloy deformation behavior changes from homogenous plastic deformation to localized shear deformation resulting in adiabatic shear bands (ASBs). At strain rates below 4779s−1, 90W–Ni–Fe alloy undergoes a homogenous deformation, and in the tungsten and γ- (Ni, Fe) phase the distribution of dislocations, dislocation tangles and the formation of substructures such as dislocation cell structures and subgrains appear randomly. Up to the strain rate of 6146s−1, an ASB with a width of about 50 μm is formed in the deformed specimen, and the microstructure in the ASBs undergoes significant dynamic recrystallization, which is more pronounced in the γ-(Ni, Fe) phase than in the tungsten phase. The evolution mechanism of the microstructure was determined through calculating the temperature rise of specimens during the deformation. A rotational dynamic recrystallization mechanism is proposed which provides a reasonable explanation for the development of the fine equiaxed grains in the ASBs. This study provides an important contribution to the design of self-sharpening tungsten alloy kinetic energy penetrators.