The study of glide dislocation loops on {001} planes in a f.c.c. alloy

Abstract

Single crystals of disordered Ni3Fe oriented for single slip were deformed in tension at room temperature. Ni3Fe represents a f.c.c. alloy in the solid solution range having both a high value of stacking fault energy γ and friction stress τf. Electron microscopy methods are used to study undissociated glide dislocations (b = a/2[110]) bowing out on (001) planes. The local radius of curvature of these half loops is rather low for dislocation characters near 35° and 90° and therefore their shape deviates from the elliptical one normally observed for glide dislocations on {111} planes in f.c.c. metals. The experimentally observed loop shapes agree very well with shapes calculated using a line tension model. From this agreement it can be concluded that τf balancing the stress of the loop does not depend on the character of the dislocation. This result is confirmed by computations showing that τf mainly arises from modulus and short-range-order (SRO) effects. Finally the values of the locally effective friction stress are determined and compared with the critical resolved shear stress.