ENHANCEMENT OF HETEROGENEOUS DEFORMATION IN FCC METALS DUE TO INTRODUCTION OF DISLOCATION LOOPS

Macroscopic and microscopic inhomogeneities in plastic deformation of quenched aluminum single crystals and polycrystals were examined by observing slip bands and dislocation structures using optical and transmission electron microscopes to make clear the enhancement of heterogeneous deformation in FCC metals due to the introduction of a large number of small dislocation loops. Main results are as follows: Both secondary and primary slip bands in single crystals appear heterogeneously along the length of crystals both in macroscopic and microscopic scales. Primary edge dislocations of the same sign are distributed in excess in coarse primary slip bands. Secondary slip bands are initiated from a point of a primary slip band and then extend into a definite direction, and dislocation structures indicating one-directional extension of multiplied secondary dislocations are observed. Secondary dislocations protruding into an area between coarse primary slip bands from coarse primary slip bands sweep away dislocation loops existing there. Shear displacement in a conjugate slip band corresponds to that expected in compressive deformation, in spite of tensile deformation. The decrease in uniform elongation is recognized to occur in quenched polycrystals.