Spallation of polycrystalline tungsten using laser-induced shock at ultrahigh strain rates

Abstract

Laser-induced shock technology was used to achieve the shock loading of polycrystalline tungsten (W) at an ultrahigh strain rate. The shock response and fracture behavior of W were investigated at different tensile strain rates. Unlike the intergranular fracture mode under quasistatic conditions, the transgranular–intergranular-mixed fracture mode of W was detected at high strain rates and the proportion of transgranular cleavage mode increased. The spall strength of W was positively correlated to the strain rate, reaching 5.86 GPa when the tensile strain rate reached 106 s−1 in the spall plane. The mobility of screw dislocations increased at high strain rates, and the simultaneous emission of screw dislocations improved the spall strength while accelerating the expansion of crack nucleation positions, inducing numerous transgranular fractures.