Microstructural properties associated with adiabatic shear bands in titanium-aluminum-vanadium deformed by ballistic impact.

摘要

The importance of adiabatic shear bands (ASBs) in material failure in terms of dynamic deformation has been the focus and interest of engineers for decades. Shear localization phenomena, ie.ASBs, is of interest is because cracks initiate and propagate along adiabatic shear bands. Many studies thus far have shown that ASBs and the dynamically recrystallized grains that compose them is what allows for plastic flow and the consequential failure of materials. This study aims to characterize microstructures within these adiabatic shear bands due to ballistic impact.;A series of electron beam melted, cold hearth, single melt Ti-6Al-4V plates were subjected to ballistic impact velocities of 633, 905, and 1027 m/s. Target samples were sectioned, polished, and prepared for optical, electron backscatter, and transmission electron microscopy to characterize microstructural properties of adiabatic shear bands.;Results showed the presence of small dynamically recrystallized grains and no evidence of phase transformations within the adiabatic shear band. TEM analysis shows the presence of many deformation structures within and around the shear band region, including twins, DRX grains, and many different dislocation structures. The abundance of dislocation structures accounts for the increase in hardness within the ASB. This study confirmed that DRX microstructures within the adiabatic shear bands is the mechanism for which extreme plastic deformation is accommodated and allows for material to flow plastically.