Oscillatory regime of metallic plate breakdown under laser beam

摘要

Abstract: Dynamics of keyhole formation in metal plates of Mo, W, Ni, stainless steel have been studied under the solid-state laser pulse effect ($lambda $EQ 1.06 $mu@m). Velocities of the keyhole bottom motion have been determined for these metals in the (0.5 $DOT 10$+5$/ - 10$+6$/) W/cm$+2$/ range of irradiated power densities. A pulse regime of plate breakdown has been found out. Small-dimensional structures with d $CNGR 1 $mu@m period were found on the keyhole walls, which, in our opinion, can contribute significantly to laser beam absorption. A new form of periodic structure has been revealed, being a helix-shaped modulation of the keyhole walls and bottom relief. Temperature variation were discovered in the keyhole, related to capillary waves propagation in the melt layer. !15