Characteristics of dynamic fracture of aluminum and metallographic analysis of recovered samples in laser experiments

High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at Shenguang-Ⅱ laser facility. The free surface velocity histories of shock-loaded samples, 150 m thick and with initial temperature from 293 K to 873 K, were recorded using velocity interferometer system for any reflector (VISAR). From the free surface velocity profile ,spall strength and yield stress are calculated, which shows that spall strength declines while yield strength increases with initial temperature increasing. The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more bigger voids near the spall plane. Meanwhile, the grain size increases with temperature slowly except the sharp change at 893K(near melting point). Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.