The real structure of crystals of the tetrahedrally close-packed alloys

High resolution electron microscopy has, with the lattice‐image technique, proved to be a powerful tool to investigate different kinds of defects in detail, expecially in oxide systems. The use of this technique was now been extended to include the so‐called tetrahedrally close‐packed alloys structures.1,2 Four different alloys containing different phases, Cr‐Fe‐Ni (σ‐), Fe‐Mo (σ‐ and μ‐), Mo‐Co‐Si (Mo3CoSi and μ‐) and Nb‐Ni‐Al (M‐), will be discussed here. The microscope used was a Philips EM 400 equipped with a H.R.G. and operating at 120 kV. Different kinds of defects were frequently observed and can be expalined with crystallographic operations and intergrowth.