The Onset and Blocking of Slip in Nickel Aluminide[001]

Abstract

TEM observations show that the slip is blocked by dislocation locking along both of the two directions in the {110} glide plane. The locking is explained by the non-planar splitting of the screw component along the three-fold line directions. HRTEM observations of the locked dislocations end-on show a compact core and rule out climb decomposition as the cause for the locking. The blocking of slip by dislocation locking along two line directions is in contrast to dislocations that are locked only along the screw orientations, and to dislocations that are not locked at all. This explains why slip is more difficult than and slips and the general absence of dislocations in NiAl crystals. An intuitive explanation for the planar core of dislocations is also given.