Impact response and dynamic strength of partially melted aluminum alloy

Solid solution treated aluminum alloy 6061 was tested in a series of planar impact experiments in which the initial sample temperature was varied between 296 and 902 K with special attention paid to the temperatures of the solid-liquid two-phase region. In the experiments, the free surface velocity histories were recorded using velocity interferometer system for any reflector (VISAR). It has been found that both the dynamic yield and the dynamic tensile strengths of the alloy decline monotonously through the two-phase domain and vanish completely as the initial sample temperature approaches 902 K and as the content of the liquid phase in the alloy approaches 20. Through the same temperature interval the plastic wave rise-time and the time interval between elastic and plastic waves behave non-monotonously and display a sharp maximum at 876 K, some 20 K above the solidus temperature of the alloy. We presently assume that the non-monotonous behavior is caused by a compressive-induced solidification of a thin liquid layer between the grains of the solid phase.