LASER-INDUCED SPALL OF ALUMINUM AND ALUMINUM ALLOYS AT HIGH STRAIN RATES

Abstract

We conducted laser‐induced spall experiments aimed at studying how a material's microstructure affects the tensile fracture characteristics at high strain rates (>106 s−1). We used the Z‐Beamlet Laser at Sandia National Laboratory to drive shocks and to measure the spall strength of aluminum targets with various microstructures. The targets were recrystallized, high‐purity aluminum (Al‐HP RX), recrystallized aluminum + 3 wt.% magnesium (Al‐3Mg RX), and cold‐worked aluminum +3 wt.% magnesium (Al‐3Mg CW). The Al‐3Mg RX and Al‐3Mg CW are used to explore the roles that solid‐solution alloying and cold‐work strengthening play in the spall process. Using a line‐VISAR (Velocity Interferometer System for Any Reflector) and analysis of recovered samples, we were able to measure spall strength and determine failure morphology in these targets. We find that the spall strength is highest for Al‐HP RX. Analysis reveals that material grain size plays a vital role in the fracture morphology and spall strength results.