On the mechanism of anomalous slip in bcc metals

The anomalous-slip behavior of bcc metals has been studied by TEM analyses of dislocation substructures developed in a [(2) over bar 920]-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(0)/2[1 (1) over bar 1] (Schmid factor = 0.5) and a(0)/2[1 (1) over bar 1] (Schmid factor = 0.167) coplanar screw dislocation arrays in the ((1) over bar 0 1) primary slip plane. The interaction between the multiplied a(0)/2[1 1 1] dislocations and pre-existing a(0)/2[1 (1) over bar 1] dislocation segments, which block the motion of the a(0)/2[1 1 1] dislocations, renders the multiplication of a(0)/2[1 (1) over bar 1] dislocations and leads to the formation of a(0)/2[1 1 1] and a(0)/2[1 (1) over bar 1] dislocation arrays on the ((1) over bar 0 1) primary slip plane. The occurrence of {0 (1) over bar 1} anomalous slip is accordingly proposed to be resulting from the mutual trapping of a(0)/2[1 1 1] and a(0)/2[1 (1) over bar1 1] coplanar dislocation arrays on the ((1) over bar 0 1) primary slip plane, which renders a cross-slip propagation of both a(0)/2[1 1 1] and a(0)/2[1 (1) over bar 1] screw dislocations from the ((1) over bar 0 1) plane onto the {0 (1) over bar 1} planes and thus activates the {0 1 (1) over bar 1} < 1 1 1 > slip systems. Published by Elsevier B.V.