On the mechanism of anomalous slip in bcc metals

摘要

The anomalous-slip behavior of bcc metals has been studied by TEM analyses of dislocation substructures developed in a [2 9 20]-oriented Mo single crystal uniaxially compressed at room temperature to a total-strain of 0.4%. It is found that the initial dislocation lines in association with "grown-in" super-jogs can act as effective sources for the formation of both a_o/2[111](Schmidfactor=0.5)anda_o/2[111](Schmid factor = 0.167) coplanar screw dislocation arrays in the (101) primary slip plane. The interaction between the multiplied a_o/2[111] dislocations and pre-existing a_o/2[111] dislocation segments, which block the motion of the ao/2[111] dislocations, renders the multiplication of a_o/2[111] dislocations and leads to the formation of a_o/2[111] and a_o/2[111] dislocation arrays on the (101) primary slip plane. The occurrence of {011} anomalous slip is accordingly proposed to be resulting from the mutual trapping of a_o/2[111] and a_o/2[111] coplanar dislocation arrays on the (101) primary slip plane, which renders a cross-slip propagation of both a_o/2[111] and a_o/2[111] screw dislocations from the (101) plane onto the (011) planes and thus activates the (011) (111) slip systems.