High-resolution transmission electron microscopy study of body-centered tetragonal Zr2Fe nanoparticle phase in Zircaloy-4 alloy and its typical crystalline defect structures

Abstract

Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy have been employed for crystallographic and microstructural characterization of nano-precipitates distributed within the α-Zr matrix of the Zircaloy-4 (Zr-4) alloy. These nano-precipitates, typically with an average length between 200 and 500 nm, have been identified as the C16-type Zr2Fe phase. A massive presence of randomly distributed planar defects, including stacking faults and sub-unit cell twins, were detected. Atomic-scale configurations of the intrinsic planar defects in the Zr2Fe nanoparticle phase were investigated, for the first time, through high-resolution TEM analysis. Results show that the stacking faults are extended on (110) planes with a displacement vector of 1/4[11¯1]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1/4[1 }\\overline{{1}} { 1]}$$\\end{document}. HRTEM observations and electron diffraction patterns acquired by specimen tilting reveal that these twin defects belong to 60° rotation twin with the rotation axis along the [110] direction. Geometric analysis based on the the TEM results reveals that the twinning plane and direction are 11¯2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1}\\overline{{1}} {2}$$\\end{document} and [33¯2]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${[3}\\overline{{3}} {2]}$$\\end{document}.