Formation of adiabatic shear bands and instability of plastic flow in Zr and Zr-Nb alloys in spherical stress waves

Abstract

Formation of adiabatic shear bands (ASBs) in different metals and alloys occurs at high strain rates and levels of stresses. The method of loading by spherical converging shock waves is the most perspective method for the investigation of the formation and evolution of the ASBs and other instabilities of the plastic flow. Spherical shock-wave recovery experiments allow to obtain extremely high stresses, substantially exceeding dynamic yield strength, as well as high strain rate at the fronts of spherical converging and diverging shock waves. Such experiments ensure the spherically-symmetric motion during the whole time of the wave processes progress up to the shut-down of the recovery device, exclude the distorting influence of the lateral and face-end unloading wave (in contrast to plane and cylindrical recovery devices), as well as the secondary effects associated with the deceleration and the entrapping of the compressed and recovered samples. Although a number of investigations has been made concerning the nature of the ASBs, the understanding of the ASBs formation and flow localization as modes of deformation is still insufficient. The purpose of the present work is to study the formation and evolution of the ASBs and the instability of plastic flow in zirconium and itsmore » alloys with 1 and 2.5wt% niobium under loading by spherical converging stress waves of different intensity.« less