Flow Strength of 6061-T6 Aluminum in the Solid, Mixed Phase, Liquid Regions

Abstract

Shock waves have been used to determine material properties under high shock stresses and very-high loading rates. The objectives of the present experiments were to obtain information on the mechanical response of aluminum at shock stresses approaching and in the solid–liquid mixed phase regions, which is not routinely available with other methods. The accurate determination of compressive strength under shock compression has proven to be difficult due to the need for accurate reshock experiments from the initial shock state, with the consequence that estimates of shear strength have been limited to relatively low stresses. In this investigation, we have significantly improved the shock/reloading technique to obtain high quality data on reloading from the shocked states for initial shock stresses up to about 80 GPa. This has allowed the first self-consistent determination of the shear strength and the initial shear stress state of aluminum in the shocked state in this stress region. In addition, unloading experiments have been extended to over 140 GPa to understand how the strength of the material behaves when shocked beyond the solid–liquid mixed phase boundary. The combined wave velocity and strength data provide estimates of the onset and completion of shock-induced melting.