Diffraction contrast from platelet precipitates in chromium

Abstract

Abstract Two types of planar defect have been observed in electron micrographs from high-purity chromium which had been warm-worked and then annealed in the range 1050°-1250°c, viz. (A) isolated discs 2-8 × 10s Å in in diameter, containing a central core surrounded by a dislocation tangle and (B) discs associated with loops on dislocation lines. In each case the images showed strong fringed contrast in appropriate orientations. The Type A defects are believed to be thin platelets of precipitate (probably Cr2N) of {100} habit and the fringes arise from a stacking-fault type contrast, due to lattice displacements both normal and parallel to the platelet. Insufficient evidence is available at present to identify the Type B defects.