Deformation modes and structure evolution in laser-shock-loaded molybdenumsingle crystals of high purity

This paper reports on the microstructural changes occurring within molybden um single crystals after shock treatment with an excimer laser-system in a confined ablation mode with different number of impacts. Using different co mplementary investigation methods (optical microscopy, scanning electron mi croscopy and transmission electron microscopy) it is found that slip and tw inning are active modes of deformation during the shock-induced plastic def ormation. After laser treatment with a single laser pulse slip bands on {11 2} planes containing several microscopic twins are the dominating microstru ctural feature, whereas further laser-shock-processing leads to the formati on of a homogeneous arrangement of screw dislocations, tangles and loops. D eformation modes and microstructure in laser shocked samples prove to be qu ite similar to those of explosive shocked specimens although the laser-indu ced peak pressure is about an order of magnitude lower than that during exp losive loading. It is shown that the laser shock-induced hardening increases with increasin g number of impacts in the range from 1 to 6 impacts. This shock-induced st rengthening is correlated with the overall dislocation density.