Pyramidal Slip in Zinc Single Crystals

SECOND ORDER PYRAMIDAL SLIP IN ZINC SINGLE CRYSTALS K. H. Adams,* R. C. Blish and T. Vreeland, Jr. W. M. Keck Laboratory of Engineering Materials California Institute of Technology Pasadena, California (U.S.A.) CALT-473-18 Measurements of strain, dislocation mobility and dislocation density have been made in 99.999% zinc single crystals stressed at room temperatur~ j_n comp.!:_ession along the hexagonal axis, [0001]. Slip bands on the <1213) { 1212 }, second order pyramidal system were observed. Etch pit observations indicate that the average dislocation density increases linearly with strain. The velocity of edge dislocations in slip bands obeys the relation v = v 0 (-rh 0 )n with v = 1 in/sec , n = 8.7 , -r = 870 lb/in2 , and -r the resolved sheRr stress in lb/in2 • These observRtions together with measurements of the strain-rate sensitivity of the flow stress show that the stress dependence of the density of moving dislocations is more important than the stress dependence of the dislocation velocity as they affect the strain-rate sensitivity.